| 1. |
- Yi, Chuixiang, et al.
(författare)
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Climate control of terrestrial carbon exchange across biomes and continents
- 2010
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid-and high-latitudes, (2) a strong function of dryness at mid-and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45 degrees N). The sensitivity of NEE to mean annual temperature breaks down at similar to 16 degrees C (a threshold value of mean annual temperature), above which no further increase of CO2 uptake with temperature was observed and dryness influence overrules temperature influence.
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| 2. |
- Gaillard, R. C., et al.
(författare)
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Overall and cause-specific mortality in GH-deficient adults on GH replacement
- 2012
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Ingår i: European Journal of Endocrinology. - : Oxford University Press (OUP). - 0804-4643 .- 1479-683X. ; 166:6, s. 1069-1077
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Hypopituitarism is associated with an increased mortality rate but the reasons underlying this have not been fully elucidated. The purpose of this study was to evaluate mortality and associated factors within a large GH-replaced population of hypopituitary patients. Design: In KIMS (Pfizer International Metabolic Database) 13 983 GH-deficient patients with 69 056 patient-years of follow-up were available. Methods: This study analysed standardised mortality ratios (SMRs) by Poisson regression. IGF1 SDS was used as an indicator of adequacy of GH replacement. Statistical significance was set to P<0.05. Results: All-cause mortality was 13% higher compared with normal population rates (SMR, 1.13; 95% confidence interval, 1.04-1.24). Significant associations were female gender, younger age at follow-up, underlying diagnosis of Cushing's disease, craniopharyngioma and aggressive tumour and presence of diabetes insipidus. After controlling for confounding factors, there were statistically significant negative associations between IGF1 SDS after 1, 2 and 3 years of GH replacement and SMR. For cause-specific mortality there was a negative association between 1-year IGF1 SDS and SMR for deaths from cardiovascular diseases (P=0.017) and malignancies (P=0.044). Conclusions: GH-replaced patients with hypopituitarism demonstrated a modest increase in mortality rate; this appears lower than that previously published in GH-deficient patients. Factors associated with increased mortality included female gender, younger attained age, aetiology and lower IGF1 SDS during therapy. These data indicate that GH replacement in hypopituitary adults with GH deficiency may be considered a safe treatment.
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| 3. |
- Niinemets, Ue., et al.
(författare)
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Estimations of isoprenoid emission capacity from enclosure studies: measurements, data processing, quality and standardized measurement protocols
- 2011
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 8:8, s. 2209-2246
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Tidskriftsartikel (refereegranskat)abstract
- The capacity for volatile isoprenoid production under standardized environmental conditions at a certain time (E-S, the emission factor) is a key characteristic in constructing isoprenoid emission inventories. However, there is large variation in published E-S estimates for any given species partly driven by dynamic modifications in E-S due to acclimation and stress responses. Here we review additional sources of variation in E-S estimates that are due to measurement and analytical techniques and calculation and averaging procedures, and demonstrate that estimations of E-S critically depend on applied experimental protocols and on data processing and reporting. A great variety of experimental setups has been used in the past, contributing to study-to-study variations in E-S estimates. We suggest that past experimental data should be distributed into broad quality classes depending on whether the data can or cannot be considered quantitative based on rigorous experimental standards. Apart from analytical issues, the accuracy of E-S values is strongly driven by extrapolation and integration errors introduced during data processing. Additional sources of error, especially in meta-database construction, can further arise from inconsistent use of units and expression bases of E-S. We propose a standardized experimental protocol for BVOC estimations and highlight basic meta-information that we strongly recommend to report with any E-S measurement. We conclude that standardization of experimental and calculation protocols and critical examination of past reports is essential for development of accurate emission factor databases.
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| 4. |
- Niinemets, Ü., et al.
(författare)
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The leaf-level emission factor of volatile isoprenoids: caveats, model algorithms, response shapes and scaling
- 2010
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 7:6, s. 1809-1832
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Tidskriftsartikel (refereegranskat)abstract
- In models of plant volatile isoprenoid emissions, the instantaneous compound emission rate typically scales with the plant's emission potential under specified environmental conditions, also called as the emission factor, ES. In the most widely employed plant isoprenoid emission models, the algorithms developed by Guenther and colleagues (1991, 1993), instantaneous variation of the steady-state emission rate is described as the product of ES and light and temperature response functions. When these models are employed in the atmospheric chemistry modeling community, species-specific ES values and parameter values defining the instantaneous response curves are often taken as initially defined. In the current review, we argue that ES as a characteristic used in the models importantly depends on our understanding of which environmental factors affect isoprenoid emissions, and consequently need standardization during experimental ES determinations. In particular, there is now increasing consensus that in addition to variations in light and temperature, alterations in atmospheric and/or within-leaf CO2 concentrations may need to be included in the emission models. Furthermore, we demonstrate that for less volatile isoprenoids, mono- and sesquiterpenes, the emissions are often jointly controlled by the compound synthesis and volatility. Because of these combined biochemical and physico-chemical drivers, specification of ES as a constant value is incapable of describing instantaneous emissions within the sole assumptions of fluctuating light and temperature as used in the standard algorithms. The definition of ES also varies depending on the degree of aggregation of ES values in different parameterization schemes (leaf- vs. canopy- or region-scale, species vs. plant functional type levels) and various aggregated ES schemes are not compatible for different integration models. The summarized information collectively emphasizes the need to update model algorithms by including missing environmental and physico-chemical controls, and always to define ES within the proper context of model structure and spatial and temporal resolution.
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| 5. |
- Fleming, Fergal J., et al.
(författare)
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Neoadjuvant Therapy in Rectal Cancer
- 2011
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Ingår i: Diseases of the Colon & Rectum. - 0012-3706 .- 1530-0358. ; 54:7, s. 901-912
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The optimal type of neoadjuvant therapy regimen in rectal cancer is contentious. OBJECTIVE: This study aimed to review the impact of neoadjuvant therapy on oncological outcomes and complications (short and long term) in patients undergoing total mesorectal excision for rectal cancer. DATA SOURCES: An electronic search of MEDLINE, PubMed, EMBASE, and the Cochrane Database of Collected Reviews was performed through March 2010. STUDY SELECTION: Key-word combinations including rectal cancer, total mesorectal excision, radiotherapy, chemotherapy, endorectal ultrasound, and magnetic resonance imaging were used to identify randomized control trials where chemotherapy and/or radiotherapy were deployed before resectional surgery. INTERVENTION(S): Patients underwent total mesorectal excision for rectal cancer who did and did not receive preoperative chemotherapy and/or radiotherapy. MAIN OUTCOME MEASURES: The main outcome measures comprised the impact of the addition of neoadjuvant therapy to total mesorectal excision on the perioperative complication rate, the pathological complete response rate, the rate of local recurrence, and long- term treatment-related complications. RESULTS: A total of 12 randomized control trials involving 9410 patients were included. Both short-course radiotherapy and long-course chemoradiation can offer a relative risk reduction of 50% in local recurrence in appropriately selected patients with stage II and III rectal cancer. This oncological benefit comes at the cost of a relative risk increase of 50% in both acute treatment-related toxicity and long-term anorectal dysfunction. LIMITATIONS: Preoperative staging provides only an estimate of the "true" tumor stage that can only be determined by histological assessment of the tumor specimen which renders appropriate patient selection challenging. CONCLUSIONS: The current treatment trade-off of a relative risk reduction of local recurrence of 50% at the cost of a relative increase of 50% in treatment-related complications underpins the need for more accurate patient staging and more precise delivery of neoadjuvant therapy.
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| 6. |
- Jardine, Kolby J., et al.
(författare)
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Within-plant isoprene oxidation confirmed by direct emissions of oxidation products methyl vinyl ketone and methacrolein
- 2012
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 18:3, s. 973-984
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Tidskriftsartikel (refereegranskat)abstract
- Isoprene is emitted from many terrestrial plants at high rates, accounting for an estimated 1/3 of annual global volatile organic compound emissions from all anthropogenic and biogenic sources combined. Through rapid photooxidation reactions in the atmosphere, isoprene is converted to a variety of oxidized hydrocarbons, providing higher order reactants for the production of organic nitrates and tropospheric ozone, reducing the availability of oxidants for the breakdown of radiatively active trace gases such as methane, and potentially producing hygroscopic particles that act as effective cloud condensation nuclei. However, the functional basis for plant production of isoprene remains elusive. It has been hypothesized that in the cell isoprene mitigates oxidative damage during the stress-induced accumulation of reactive oxygen species (ROS), but the products of isoprene-ROS reactions in plants have not been detected. Using pyruvate-2-13C leaf and branch feeding and individual branch and whole mesocosm flux studies, we present evidence that isoprene (i) is oxidized to methyl vinyl ketone and methacrolein (iox) in leaves and that iox/i emission ratios increase with temperature, possibly due to an increase in ROS production under high temperature and light stress. In a primary rainforest in Amazonia, we inferred significant in plant isoprene oxidation (despite the strong masking effect of simultaneous atmospheric oxidation), from its influence on the vertical distribution of iox uptake fluxes, which were shifted to low isoprene emitting regions of the canopy. These observations suggest that carbon investment in isoprene production is larger than that inferred from emissions alone and that models of tropospheric chemistry and biotachemistryclimate interactions should incorporate isoprene oxidation within both the biosphere and the atmosphere with potential implications for better understanding both the oxidizing power of the troposphere and forest response to climate change.
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| 7. |
- Niinemets, Ue., et al.
(författare)
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The emission factor of volatile isoprenoids: stress, acclimation, and developmental responses
- 2010
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 7:7, s. 2203-2223
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Tidskriftsartikel (refereegranskat)abstract
- The rate of constitutive isoprenoid emissions from plants is driven by plant emission capacity under specified environmental conditions (E-S, the emission factor) and by responsiveness of the emissions to instantaneous variations in environment. In models of isoprenoid emission, E-S has been often considered as intrinsic species-specific constant invariable in time and space. Here we analyze the variations in species-specific values of E-S under field conditions focusing on abiotic stresses, past environmental conditions and developmental processes. The reviewed studies highlight strong stress-driven, adaptive (previous temperature and light environment and growth CO2 concentration) and developmental (leaf age) variations in E-S values operating at medium to long time scales. These biological factors can alter species-specific E-S values by more than an order of magnitude. While the majority of models based on early concepts still ignore these important sources of variation, recent models are including some of the medium- to long-term controls. However, conceptually different strategies are being used for incorporation of these longer-term controls with important practical implications for parameterization and application of these models. This analysis emphasizes the need to include more biological realism in the isoprenoid emission models and also highlights the gaps in knowledge that require further experimental work to reduce the model uncertainties associated with biological sources of variation.
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