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- Arndt, D. S., et al.
(författare)
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STATE OF THE CLIMATE IN 2017
- 2018
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Ingår i: Bulletin of The American Meteorological Society - (BAMS). - : American Meteorological Society. - 0003-0007 .- 1520-0477. ; 99:8, s. S1-S310
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Forskningsöversikt (refereegranskat)
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- Duncanson, Laura, et al.
(författare)
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Aboveground biomass density models for NASA's Global Ecosystem Dynamics Investigation (GEDI) lidar mission
- 2022
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Ingår i: Remote Sensing of Environment. - : Elsevier BV. - 0034-4257 .- 1879-0704. ; 270
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Tidskriftsartikel (refereegranskat)abstract
- NASA's Global Ecosystem Dynamics Investigation (GEDI) is collecting spaceborne full waveform lidar data with a primary science goal of producing accurate estimates of forest aboveground biomass density (AGBD). This paper presents the development of the models used to create GEDI's footprint-level (~25 m) AGBD (GEDI04_A) product, including a description of the datasets used and the procedure for final model selection. The data used to fit our models are from a compilation of globally distributed spatially and temporally coincident field and airborne lidar datasets, whereby we simulated GEDI-like waveforms from airborne lidar to build a calibration database. We used this database to expand the geographic extent of past waveform lidar studies, and divided the globe into four broad strata by Plant Functional Type (PFT) and six geographic regions. GEDI's waveform-to-biomass models take the form of parametric Ordinary Least Squares (OLS) models with simulated Relative Height (RH) metrics as predictor variables. From an exhaustive set of candidate models, we selected the best input predictor variables, and data transformations for each geographic stratum in the GEDI domain to produce a set of comprehensive predictive footprint-level models. We found that model selection frequently favored combinations of RH metrics at the 98th, 90th, 50th, and 10th height above ground-level percentiles (RH98, RH90, RH50, and RH10, respectively), but that inclusion of lower RH metrics (e.g. RH10) did not markedly improve model performance. Second, forced inclusion of RH98 in all models was important and did not degrade model performance, and the best performing models were parsimonious, typically having only 1-3 predictors. Third, stratification by geographic domain (PFT, geographic region) improved model performance in comparison to global models without stratification. Fourth, for the vast majority of strata, the best performing models were fit using square root transformation of field AGBD and/or height metrics. There was considerable variability in model performance across geographic strata, and areas with sparse training data and/or high AGBD values had the poorest performance. These models are used to produce global predictions of AGBD, but will be improved in the future as more and better training data become available.
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- Abernethy, R. J., et al.
(författare)
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Poly(methimazolyl)borato nitrosyl complexes of molybdenum and tungsten
- 2008
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Ingår i: Organometallics. - : American Chemical Society (ACS). - 0276-7333 .- 1520-6041. ; 27:17, s. 4455-4463
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Tidskriftsartikel (refereegranskat)abstract
- The syntheses of a range of poly(methimazolyl)borate -ligated nitrosyl complexes of tungsten and molybdenum are reported, the characterization of which includes the crystal structure determinations of the compounds [W(NO)(CO)(2){k(3)-S,S',S''-HB(mt)(3)}], [W(NO)(CO)(2)(PPh3){k(2)-S,S'-H2B(mt)(2)}], and [Mo(NO-)(CO)(2) {k(3)-H,S,S'-H2B(mt)(2)}] (mt = methimazoyl). The reaction of [W(NO)(CO)(3)(PPh3)(2)]PF6 with Na[HB(mt)(3)] and Na[H2B(mt)(2)}] provides respectively [W(NO)(CO)(2)[HB(mt)(3)] and [W(NO)(CO)(2)(PPh3){k(2_) S,S'-H2B(mt)(2)}]. The complexes [M(NO)(CO)(2){HB(mt)(3)}] and [M(NO)(CO)(2){k(3)-H,S,S'-H2B(mt)(2)}] (M = W, Mo) arise from the reactions of Na[M(CO)(3){H2B(mt)(2)}] with N-methyl-N-nitrosotoluenesulfonamide. The molybdenum complex [Mo(NO)(CO)(2){HB(mt)(3)}] is also obtained unexpectedly from the reaction of [MO(eta(3)-C3H5)(CO)(2){HB(mt)(3)}] with [NO]BF4.
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- Hess, Connie N., et al.
(författare)
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Relationship Between Cancer and Cardiovascular Outcomes Following Percutaneous Coronary Intervention
- 2015
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Ingår i: Journal of the American Heart Association. - 2047-9980 .- 2047-9980. ; 4:7
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Tidskriftsartikel (refereegranskat)abstract
- Background-Cardiovascular disease and cancer increasingly coexist, yet relationships between cancer and long-term cardiovascular outcomes post-percutaneous coronary intervention (PCI) are not well studied. Methods and Results-We examined stented PCI patients at Duke (1996-2010) using linked data from the Duke Information Systems for Cardiovascular Care and the Duke Tumor Registry (a cancer treatment registry). Our primary outcome was cardiovascular mortality. Secondary outcomes included composite cardiovascular mortality, myocardial infarction, or repeat revascularization and all-cause mortality. We used adjusted cause-specific hazard models to examine outcomes among cancer patients (cancer treatment pre-PCI) versus controls (no cancer treatment pre-PCI). Cardiovascular mortality was explored in a cancer subgroup with recent (within 1 year pre-PCI) cancer and in post-PCI cancer patients using post-PCI cancer as a time-dependent variable. Among 15 008 patients, 3.3% (n=496) were cancer patients. Observed rates of 14-year cardiovascular mortality (31.4% versus 27.7%, P=0.31) and composite cardiovascular death, myocardial infarction, or revascularization (51.1% versus 55.8%, P=0.37) were similar for cancer versus control groups; all-cause mortality rates were higher (79.7% versus 49.3%, P<0.01). Adjusted risk of cardiovascular mortality was similar for cancer patients versus controls (hazard ratio 0.95; 95% CI 0.76 to 1.20) and for patients with versus without recent cancer (hazard ratio 1.46; 95% CI 0.92 to 2.33). Post-PCI cancer, present in 4.3% (n=647) of patients, was associated with cardiovascular mortality (adjusted hazard ratio 1.51; 95% CI 1.11 to 2.03). Conclusions-Cancer history was present in a minority of PCI patients but was not associated with worse long-term cardiovascular outcomes. Further investigation into PCI outcomes in this population is warranted.
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- Huaraca Huasco, Walter, et al.
(författare)
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Fine root dynamics across pantropical rainforest ecosystems
- 2021
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Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 27:15, s. 3657-3680
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Tidskriftsartikel (refereegranskat)abstract
- Fine roots constitute a significant component of the net primary productivity (NPP) of forest ecosystems but are much less studied than aboveground NPP. Comparisons across sites and regions are also hampered by inconsistent methodologies, especially in tropical areas. Here, we present a novel dataset of fine root biomass, productivity, residence time, and allocation in tropical old-growth rainforest sites worldwide, measured using consistent methods, and examine how these variables are related to consistently determined soil and climatic characteristics. Our pantropical dataset spans intensive monitoring plots in lowland (wet, semi-deciduous, and deciduous) and montane tropical forests in South America, Africa, and Southeast Asia (n = 47). Large spatial variation in fine root dynamics was observed across montane and lowland forest types. In lowland forests, we found a strong positive linear relationship between fine root productivity and sand content, this relationship was even stronger when we considered the fractional allocation of total NPP to fine roots, demonstrating that understanding allocation adds explanatory power to understanding fine root productivity and total NPP. Fine root residence time was a function of multiple factors: soil sand content, soil pH, and maximum water deficit, with longest residence times in acidic, sandy, and water-stressed soils. In tropical montane forests, on the other hand, a different set of relationships prevailed, highlighting the very different nature of montane and lowland forest biomes. Root productivity was a strong positive linear function of mean annual temperature, root residence time was a strong positive function of soil nitrogen content in montane forests, and lastly decreasing soil P content increased allocation of productivity to fine roots. In contrast to the lowlands, environmental conditions were a better predictor for fine root productivity than for fractional allocation of total NPP to fine roots, suggesting that root productivity is a particularly strong driver of NPP allocation in tropical mountain regions.
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