| 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. |
- Groenendijk, M., et al.
(författare)
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Assessing parameter variability in a photosynthesis model within and between plant functional types using global Fluxnet eddy covariance data
- 2011
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Ingår i: Agricultural and Forest Meteorology. - : Elsevier BV. - 1873-2240 .- 0168-1923. ; 151:1, s. 22-38
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Tidskriftsartikel (refereegranskat)abstract
- The vegetation component in climate models has advanced since the late 1960s from a uniform prescription of surface parameters to plant functional types (PFTs) PFTs are used in global land-surface models to provide parameter values for every model grid cell With a simple photosynthesis model we derive parameters for all site years within the Fluxnet eddy covariance data set We compare the model parameters within and between PFTs and statistically group the sites Fluxnet data is used to validate the photosynthesis model parameter variation within a PFT classification Our major result is that model parameters appear more variable than assumed in PFTs Simulated fluxes are of higher quality when model parameters of individual sites or site years are used A simplification with less variation in model parameters results in poorer simulations This indicates that a PFT classification Introduces uncertainty in the variation of the photosynthesis and transpiration fluxes Statistically derived groups of sites with comparable model parameters do not share common vegetation types or climates A simple PFT classification does not reflect the real photosynthesis and transpiration variation Although site year parameters give the best predictions the parameters are generally too specific to be used in a global study The site year parameters can be further used to explore the possibilities of alternative classification schemes (C) 2010 Elsevier B V All rights reserved
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| 3. |
- Groenendijk, M., et al.
(författare)
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Seasonal variation of photosynthetic model parameters and leaf area index from global Fluxnet eddy covariance data
- 2011
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Ingår i: Journal of Geophysical Research. - 2156-2202. ; 116, s. 04027-04027
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Tidskriftsartikel (refereegranskat)abstract
- Global vegetation models require the photosynthetic parameters, maximum carboxylation capacity (V(cm)), and quantum yield (alpha) to parameterize their plant functional types (PFTs). The purpose of this work is to determine how much the scaling of the parameters from leaf to ecosystem level through a seasonally varying leaf area index (LAI) explains the parameter variation within and between PFTs. Using Fluxnet data, we simulate a seasonally variable LAI(F) for a large range of sites, comparable to the LAI(M) derived from MODIS. There are discrepancies when LAI(F) reach zero levels and LAI(M) still provides a small positive value. We find that temperature is the most common constraint for LAI(F) in 55% of the simulations, while global radiation and vapor pressure deficit are the key constraints for 18% and 27% of the simulations, respectively, while large differences in this forcing still exist when looking at specific PFTs. Despite these differences, the annual photosynthesis simulations are comparable when using LAI(F) or LAIM (r(2) = 0.89). We investigated further the seasonal variation of ecosystem-scale parameters derived with LAI(F). V(cm) has the largest seasonal variation. This holds for all vegetation types and climates. The parameter alpha is less variable. By including ecosystem-scale parameter seasonality we can explain a considerable part of the ecosystem-scale parameter variation between PFTs. The remaining unexplained leaf-scale PFT variation still needs further work, including elucidating the precise role of leaf and soil level nitrogen.
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| 4. |
- Niu, Shuli, et al.
(författare)
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Thermal optimality of net ecosystem exchange of carbon dioxide and underlying mechanisms.
- 2012
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 194:3, s. 775-783
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Tidskriftsartikel (refereegranskat)abstract
- • It is well established that individual organisms can acclimate and adapt to temperature to optimize their functioning. However, thermal optimization of ecosystems, as an assemblage of organisms, has not been examined at broad spatial and temporal scales. • Here, we compiled data from 169 globally distributed sites of eddy covariance and quantified the temperature response functions of net ecosystem exchange (NEE), an ecosystem-level property, to determine whether NEE shows thermal optimality and to explore the underlying mechanisms. • We found that the temperature response of NEE followed a peak curve, with the optimum temperature (corresponding to the maximum magnitude of NEE) being positively correlated with annual mean temperature over years and across sites. Shifts of the optimum temperature of NEE were mostly a result of temperature acclimation of gross primary productivity (upward shift of optimum temperature) rather than changes in the temperature sensitivity of ecosystem respiration. • Ecosystem-level thermal optimality is a newly revealed ecosystem property, presumably reflecting associated evolutionary adaptation of organisms within ecosystems, and has the potential to significantly regulate ecosystem-climate change feedbacks. The thermal optimality of NEE has implications for understanding fundamental properties of ecosystems in changing environments and benchmarking global models.
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| 5. |
- Wohlfahrt, Johan C., et al.
(författare)
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Microcomputed tomographic and histologic analysis of animal experimental degree II furcation defects treated with porous titanium granules or deproteinized bovine bone
- 2012
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Ingår i: Journal of Periodontology. - : Wiley. - 0022-3492 .- 1943-3670. ; 83, s. 211-221
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Tidskriftsartikel (refereegranskat)abstract
- Background: Titaniumis an interesting material for osseous reconstruction given its thrombogenic properties. The aim of this study is to compare the potential of porous titaniumgranules (PTGs) with sham and deproteinized bovine bone mineral (DBBM) in the reconstructive treatment of surgically created buccal, degree II furcation defects in mini-pigs. Methods: Buccal degree II furcation defects were surgically created in maxillary premolar teeth in adult, female, mini-pigs and filled with PTG or DBBM or were left empty (sham). After 6 weeks of healing, pigs were euthanized. Teeth with defects were excised en bloc and analyzed by microcomputed tomography (microCT) and histology. Results: The histologic analysis showed significantly more vertical bone formation in both PTG and sham groups compared to DBBM-treated defects (P <0.01). The microCT analysis showed significantly more bucco-palatal bone formation in furcations treated with PTG compared to the DBBM and sham (P <0.05). Bucco-palatal cylindrical microCT cores demonstrated a median defect fill of 96.8% for PTG-implanted defects, which was significantly greater than sham (72.2%) and DBBM (62.0%) (P <0.001) treatments. Significantly more regenerated periodontal ligament was seen for sham than DBBM-treated defects (P <0.05). Root resorption lacunae were small and infrequent and did not differ among groups. Conclusions: The results of this study in mini-pigs suggest that PTG may integrate well in alveolar bone and supports osseous regrowth in degree II furcation defects. Moreover, PTG seems safe to use in close proximity to root surfaces. Clinical studies will be necessary to further explore these experimental animal findings.
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| 6. |
- Biggar, Robert J, et al.
(författare)
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Digoxin use and the risk of breast cancer in women
- 2011
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Ingår i: Journal of Clinical Oncology. - : American Society of Clinical Oncology. - 0732-183X .- 1527-7755. ; 29:16, s. 2165-2170
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE Digoxin resembles estrogen chemically and may have estrogenic effect. We hypothesized that digoxin use might increase breast cancer incidence and examined if use might be associated with risk of breast cancer, categorized by estrogen receptor (ER) status. To determine if being under care for heart disease biased the findings, rate ratios in users of angina drugs were similarly evaluated as a control exposure group. PATIENTS AND METHODS Women using digoxin and angina drugs were identified in the nationwide Danish Prescription Database, available between 1995 and 2008. Incident breast cancers were identified in the Danish Cancer Registry and further classifying by ER status. Relative risks (RR) were compared to nonusers using age- and period-adjusted incidence rate ratios. RESULTS Two thousand one hundred forty-four of 104,648 women using digoxin developed breast cancer. Current digoxin users were at increased risk of breast cancer (RR, 1.39; 95% CI, 1.32 to 1.46), but risk was not increased in former users (RR, 0.91; 95% CI, 0.83 to 1.00). The increased risks in digoxin users were marginally higher for ER-positive breast cancers (RR, 1.35; 95% CI, 1.26 to 1.45) and ER unknown breast cancers (RR, 1.51; 95% CI, 1.38 to 1.64) than for ER-negative breast cancers (RR, 1.20; 95% CI, 1.03 to 1.40). Among 137,493 women exposed to angina drugs only (a comparison group with cardiovascular disease; n = 2,658 breast cancers), incidence was not increased in current or former users. CONCLUSION Women currently using digoxin had a significantly increased risk of breast cancer. Risk normalized when digoxin was stopped. No risk increases were observed in women using angina drugs only. The higher risk of developing ER-positive breast cancers supports an estrogen-mimicking mechanism.
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| 7. |
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| 8. |
- Mueller-Wohlfahrt, H. W., et al.
(författare)
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Terminology and classification of muscle injuries in sport: The Munich consensus statement
- 2013
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Ingår i: British Journal of Sports Medicine. - : BMJ. - 0306-3674 .- 1473-0480. ; 47:6
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Tidskriftsartikel (refereegranskat)abstract
- Objective To provide a clear terminology and classification of muscle injuries in order to facilitate Methods Thirty native English-speaking scientists and team doctors of national and first division Results The response rate of the survey was 63%. The responses confirmed the marked variability in Conclusions A consistent English terminology as well as a comprehensive classification system for What are the new things Consensus definitions of the terminology which is used in the field of muscle
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| 9. |
- Verket, A., et al.
(författare)
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Maxillary Sinus Augmentation with Porous Titanium Granules: A Microcomputed Tomography and Histologic Evaluation of Human Biopsy Specimens
- 2013
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Ingår i: International Journal of Oral & Maxillofacial Implants. - 0882-2786. ; 28:3, s. 721-728
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The aim of this study was to assess bone ingrowth into porous titanium granules used for maxillary sinus augmentation. Materials and Methods: Eighteen biopsy specimens from 17 patients participating in a clinical trial on sinus augmentation using porous titanium granules (PTG) were received in the laboratory. The specimens (trephine cores of 4.5 mm) were obtained 6 months after PTG placement. After being embedded in methacrylate, the samples were scanned in a microcomputed tomography (micro-CT) scanner. Specimens were then cut along the long axis and central slices were ground to 70 mu m before staining with hematoxylin and eosin. Results: The micro-CT analysis demonstrated an average bone fill of 19% (standard deviation [SD] 5.8%), whereas the graft material occupied 22.7% (SD 4.7%). The volume of newly formed bone decreased with the distance from the residual bone of the sinus floor. Two-dimensional histomorphometric analysis demonstrated a mean area of new bone of 16.1% (SD 9.4%). The PTG alone occupied 25.9% of the total mean area (SD 6.1%). The newly formed bone consisted mainly of woven bone growing in close contact with the granules and bridging the intergranular space. The remaining area was occupied predominantly by nonmineralized connective tissue. There were no signs of inflammation in any of the biopsy specimens. Conclusions: After 6 months, new bone had formed at a similar rate and quality as has been reported for other well-recognized bone graft substitutes. The new bone formed in close contact with the PTG, suggesting that the material is osteoconductive.
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