African American patients frequently receive nonstandard treatment and demonstrate poorer overall survival (OS) outcomes compared to White patients. Our objective was to analysis whether racial/ethnic disparities in rectal cancer-specific mortality remain after accounting for clinical characteristics, treatment, and access-to-care-related factors.
Rising atmospheric CO2 concentration (C a) is expected to accelerate tree growth by enhancing photosynthesis and increasing intrinsic water-use efficiency (iWUE). However, the extent of this effect on long-term iWUE and its interactions with climate remains unclear in trees along an elevation gradient. Therefore, we investigated the variation in the radial growth and iWUE of mature Picea schrenkiana trees located in the upper tree-line (A1: 2700 m a.s.l.), middle elevation (A2: 2400 m a.s.l.), and lower forest limit (A3: 2200 m a.s.l.), in relation to the rising C a and changing climate in the Wusun Mountains of northwestern China, based on the basal area increment (BAI) and tree-ring δ(13)C chronologies from 1960 to 2010. We used the CRU TS3.22 dataset to analyze the general response of tree growth to interannual variability of regional climate, and found that BAI and δ(13)C are less sensitive to climate at A1 than at A2 and A3. The temporal trends of iWUE were calculated under three theoretical scenarios, as a baseline for interpreting the observed gas exchange at increasing C a. We found that iWUE increased by 12-32% from A1 to A3 over the last 50 years, and showed an elevation-dependent variation in physiological response. The significant negative relationship between BAI and iWUE at A2 and A3 showed that tree growth has been decreasing despite long-term increases in iWUE. However, BAI remained largely stable throughout the study period despite the strongest iWUE increase [at constant intercellular CO2 concentration (C i) before 1980] at A1. Our results indicate a drought-induced limitation of tree growth response to rising CO2 at lower elevations, and no apparent change in tree growth and diminished iWUE improvement since 1980 in the upper tree-line. This study may contradict the expectation that combined effects of elevated C a and rising temperatures have increased forest productivity, especially in high-elevation forests.
ABSTRACT We developed an annual tree‐ring δ 18 O chronology from Larix sibirica in the eastern Tianshan Mountains of northwestern China. Climatic response revealed that tree‐ring δ 18 O was significantly positively correlated with the mean and maximum July–August temperatures, whereas the July precipitation and relative humidity were significantly negatively correlated with tree‐ring δ 18 O . The self‐calibrating Palmer drought severity index (sc_PDSI) in July–August was significantly correlated with the tree‐ring δ 18 O , which reflects the comprehensive effects of the three parameters on tree‐ring δ 18 O fractionation. We established a robust reconstruction of July–August sc_ PDSI that accounted for 38.4% of the total variance of sc_PDSI from 1959 to 2008. The sc_PDSI reconstruction yields new insights on past drought that were not previously realized in other PDSI reconstructions (e.g. Monsoon Asia Drought Atlas) from the region. The reconstruction revealed several wet and dry periods but no trend towards a wetter climate in the eastern Tianshan Mountains during the last two decades. It also detected synergistic effects of the North Atlantic Oscillation and the El Niño‐Southern Oscillation on regional moisture conditions as a result of teleconnections between tropical oceans and mid‐latitude circulation patterns.
In order to decrease influences of increase in air temperature and engineering disturbance on the permafrost underground, dry bridge, also named as bridge instead of embankment, is adopted along the Qinghai-Tibet Railroad according to different earth temperature and ice content at permafrost regions. Shaking table tests for scale model of pile foundation were executed and the characteristics of seismic response of the piles were analyzed. On the basis of the tests, the characteristics of dynamic response of pile foundation of Qingshui River Bridge were analyzed by dynamic finite element analysis. It is of current significance for research on the quantitative effects of dynamic load on pile foundation deformation at permafrost regions and for safe operation of the Qinghai-Tibet Railroad.
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