| 1. |
- Farahat, Emad, et al.
(författare)
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Are standing dead trees (snags) suitable as climate proxies? A case study from the central Scandinavian Mountains
- 2018
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 33:2, s. 114-124
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 Informa UK Limited, trading as Taylor & Francis Group Standing dead trees (snags) play important roles in forest ecology by storing carbon as well as providing habitats for many species. Moreover, snags preserved for hundreds of years can provide useful data to extend tree-ring chronologies used for climatological and ecological studies beyond the lifespans of living trees. Here we examined the growth patterns of Scots pine snags from the central Scandinavian Mountains, in relation to still living trees. Using changes point analyses, we showed that a majority (74%) of the snags displayed significant negative growth changes prior (on average 17 years) to death. Change points around the same years were also seen in living trees, but they recovered their growth. The average growth reduction of snags showing negative growth changes before death was 46%. In most cases the final growth change points coincided with very cold summers, or to a lesser degree to period of cool summers. It was suggested that pines ending up as snags were less resilient than the trees which continued living, and thus not able to recover after cold summer events. Since the snag growth reductions prior to death were partly unrelated to climate, care should be taken when using such data in dendroclimatological studies.
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| 2. |
- Hammarström, L-E, et al.
(författare)
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Endoscopic sphincterotomy for bile duct calculi: factors influencing the success rate. Hepato-Gastroenterol 1996; 43: 127-133.
- 1996
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Ingår i: Hepato-Gastroenterology. - 0172-6390. ; 43:7, s. 127-133
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND/AIMS: Endoscopic sphincterotomy is an established treatment of retained or recurrent common bile duct calculi after cholecystectomy and in the majority of patients with an intact gallbladder. In order to identify patients ultimately requiring additional endoscopic procedures or surgery, factors predictive of decreased endoscopic bile duct clearance were sought. MATERIAL AND METHODS: Between 1981 and 1992 endoscopic sphincterotomy was performed in 393 consecutive patients with either intact gallbladders (n = 246), recurrent (n = 92) or retained (n = 55) calculi. RESULTS: There was a 9.4% overall early complication rate for the procedure and a 30-day mortality rate of 0.5% (two patients, non-procedure related). Complete removal of all bile duct calculi failed in 35/393 patients (8.9%). In patients with intact gallbladder the clearance rate at first attempt was higher (p = 0.002; Chi-square test) in the presence of solitary as compared to multiple stones. The same was found in patients with recurrent stones as well (p < 0.001). In non-cholecystectomized patients with single or multiple stones smaller than 10 mm, the clearance rate was higher at first (p = 0.02) as well as at final (p < 0.002) attempt as compared to patients with larger stones. Single small ( < 10 mm) compared to single large stones in patients with intact gallbladder had a higher clearance rate at final (p = 0.002) but not at first (p = 0.18) attempt. Patients with intact gallbladder and pancreatitis had higher clearance rate at first attempt compared to patients with jaundice (p = 0.001) or patients without concomitant pancreatobiliary disease (p = 0.002). Clearance rate was the same in patients with and without endoscopic sphincterotomy complications, except for patients with basket impaction, in whom the clearance rate was decreased (p = 0.02). CONCLUSIONS: Thus, in patients with intact gallbladder surgery should be considered after failed complete bile duct clearance at first attempt.
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| 3. |
- Hannesson, P H, et al.
(författare)
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Transhepatic intravascular ultrasound for evaluation of portal venous involvement in patients with cancer of the pancreatic head region.
- 2002
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Ingår i: European Radiology. - : Springer Science and Business Media LLC. - 0938-7994 .- 1432-1084. ; 12:5, s. 1150-1154
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the ability of intravascular ultrasound to diagnose tumor involvement of the portal and the superior mesenteric veins using the preoperative percutaneous, transhepatic approach, and to compare the findings with those made at concomitant direct portography, surgery, and histopathological examination. Ten patients with a preoperative diagnosis of a resectable tumor in the pancreatic head region were examined with percutaneous transhepatic portography (PTP) and intravascular ultrasound (IVUS). The surgeon's intraoperative evaluation and the histopathological examination in combination revealed tumor involvement of the portal or superior mesenteric veins in six of the ten patients. Percutaneous transhepatic portography suggested tumor involvement of the veins in six patients but two of the examinations were false positive and another two were false negative. Intravascular ultrasound showed signs of tumor involvement in eight patients. The examination was, however, false positive in two patients, but there were no false negatives. Complications of the percutaneous transhepatic procedure occurred in six patients including severe pain, bleeding, and related death. Percutaneous transhepatic IVUS of the portal vein may be a useful tool in the preoperative selection of the subgroup of patients with tumor of the pancreatic head region that could benefit from surgery. There is a need for technical improvement as well as studies with larger patient series to definitely decide the role of the technique.
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| 4. |
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| 5. |
- Linderholm, Hans W., 1968, et al.
(författare)
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Growth dynamics of tree-line and lake-shore Scots pine (Pinus sylvestris L.) in the central Scandinavian Mountains during the Medieval Climate Anomaly and the early Little Ice Age
- 2014
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Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- Trees growing at their altitudinal or latitudinal distribution in Fennoscandia have been widely used to reconstruct warm season temperatures, and the region hosts some of the world’s longest tree-ring chronologies. These multi-millennial long chronologies have mainly been built from tree remains found in lakes (subfossil wood from lake-shore trees). We used a unique dataset of Scots pine tree-ring data collected from wood remains found on a mountain slope in the central Scandinavian Mountains, yielding a chronology spanning over much of the last 1200 years. This data was compared with a local subfossil wood chronology with the aim to 1) describe growth variability in two environments during the Medieval Climate Anomaly (MCA) and the early Little Ice Age (LIA), and 2) investigate differences in growth characteristics during these contrasting periods. It was shown that the local tree-line during both the MCA and early LIA was almost 150 m higher that at present. Based on living pines from the two environments, tree-line pine growth was strongly associated with mid-summer temperatures, while the lake-shore trees showed an additional response to summer precipitation. During the MCA, regarded to be a period of favourable climate in the region, the tree-ring data from both environments showed strong coherency and moderate growth variability. In the early LIA, the two chronologies were less coherent, with the tree-line chronology showing more variability, suggesting different growth responses in the two environments during this period of less favourable growing conditions. Our results indicate that tree-ring width chronologies mainly based on lake-shore trees may need to be reevaluated.
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| 8. |
- Stridbeck, Petter, et al.
(författare)
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Partly decoupled tree-ring width and leaf phenology response to 20th century temperature change in Sweden
- 2022
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Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 75
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Tidskriftsartikel (refereegranskat)abstract
- The recent warming trend, and associated shifts in growing season length, challenge the principle of uniformitarianism, i.e., that current relations are persistent over time, and complicates the uncritical inferences of past climate from tree-ring data. Here we conduct a comparison between tree-ring width chronologies of Pinus sylvestris L. (Scots pine), Picea abies (L.) Karst. (Norway spruce) and Betula pubescens Ehrh. (Downy birch) and phenological observations (budburst and leaf senescence) of Fagus sylvatica L. (European beech), Quercus robur L. (European oak), Betula sp. (Birch), Norway spruce and Scots pine) in Sweden to assess to what extent the tree-ring width–temperature relationship and the timing of phenological phases are affected by increased temperature. Daily meteorological observations confirm a prolongation of the thermal growing season, most consistently observed as an earlier onset of around 1–2 weeks since the beginning of the 20th century. Observations of budburst closely mimic this pattern, with budburst of the deciduous trees occurring 1–2.5 weeks earlier. In contrast to the changes seen in phenology and observational temperature data, the tree-ring width–temperature relationships remain surprisingly stable throughout the 20th century. Norway spruce, Scots pine and Downy birch all show consistently significant correlations with at least one 30 day-long window of temperature starting in late June–early July season. Norway spruce displays the largest degree of stability, with a consistent 60 day-long temperature window with significant correlation starting around Julian calendar day 150. Thus, our results suggest that the principle of uniformitarianism is not violated during the period covered by modern meteorological observations. Further research is needed to determine at what thresholds the temperature sensitivity of these species may alter or deteriorate as a consequence of the ongoing climate change.
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