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- Krebs, C. J., et al.
(författare)
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Terrestrial trophic dynamics in the Canadian Arctic
- 2003
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Ingår i: Canadian Journal of Zoology-Revue Canadienne De Zoologie. ; 81, s. 827-843
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Tidskriftsartikel (refereegranskat)abstract
- The Swedish Tundra Northwest Expedition of 1999 visited 17 sites throughout the Canadian Arctic. At 12 sites that were intensively sampled we estimated the standing crop of plants and the densities of herbivores and predators with an array of trapping, visual surveys, and faecal-pellet transects. We developed a trophic-balance model using ECOPATH to integrate these observations and determine the fate of primary and secondary production in these tundra ecosystems, which spanned an 8-fold range of standing crop of plants. We estimated that about 13% of net primary production was consumed by herbivores, while over 70% of small-herbivore production was estimated to flow to predators. Only 9% of large-herbivore production was consumed by predators. Organization of Canadian Arctic ecosystems appears to be more top-down than bottom-up. Net primary production does not seem to be herbivore-limited at any site. This is the first attempt to integrate trophic dynamics over the entire Canadian Arctic.
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- Brus, E, et al.
(författare)
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Bed Material Consumption in Biomass Fired Fluidised Bed Boilers Due to Risk of Bed Agglomeration : Coating Formation and Possibilities for Regeneration
- 2003
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Ingår i: Industrial Combustion. - 2075-3071. ; :2, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies have shown that many biomass fuels result in critical agglomeration temperatures in the same range as typical operating process temperatures for fluidised beds. As soon as a sufficiently thick coating on the bed particles has been formed, the risk for severe agglomeration and defluidisation is often significant. Frequent bed change is therefore the normally method applied to ensure problem-free operation, but this is associated with additional costs and not sustainable on a long-term basis.The objectives of the present work were therefore to; i) collect full-scale bed material samples to determine coating characteristics and growth as functions of time; ii) estimate the critical coating thickness/age of the bed particles by SEM/EDS analysis and experimental determinate the agglomeration temperatures for the collected bed material; iii) experimentally evaluate if size fractionation and mechanical treatment could be used to reduce the bed material consumption.Bed material samples from two bubbling and two circulating full-scale fluidised bed boilers, with previous documented bed agglomeration problems, were collected. All plants used typical wood-based fuel mixtures. The coating formation rates on the bed particles were found to be significant, with an initial rate of some mm per day, but decreasing with time. The coating material was generally found to consist of Ca- and Mg-silicates as well as P, although the form in which it was present was not determined. The experimentally determined fuel specific agglomeration temperatures were found to agree well with the corresponding critical temperatures for the full-scale bed materials, as well as with the experiences reported by the different plant operators. The critical coating thickness was found to be relatively thin (
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- Johansson, Anders, et al.
(författare)
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Wound infiltration with ropivacaine and fentanyl: Effects on postoperative pain and PONV after breast surgery
- 2003
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Ingår i: Journal of Clinical Anesthesia. - 1873-4529. ; 15:2, s. 113-118
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Tidskriftsartikel (refereegranskat)abstract
- Study Objective: To determine whether Postoperative wound infiltration with local anesthetics combined with fentanyl improves analgesia following breast surgery; and to investigate awakening and Postoperative nausea/vomiting. Design: Prospectively randomized clinical study. Setting: University hospital. Patients: 45 ASA physical status I and II patients scheduled for breast surgery. Interventions: Patients were prospectively randomized and assigned to one of three treatments during general anesthesia: postsurgical wound infiltration with ropivacaine 0.375%; wound infiltration with ropivacaine 0.375% combined with fentanyl 0.5 mug/kg; and intravenous (IV) fentanyl 0.5 mug/kg before skin incision and no wound infiltration. Time to first verbal response, Pain at rest, Postoperative nausea and vomiting, and ketobemidone and dixyrazine utilization were compared. Measurements and Main Results: Time to first verbal response was significantly shorter in the IV fentanyl group compared to both infiltration groups (8.1 +/- 4.5 min vs. 15.3 +/- 4.3, and 12.0 +/- 5.0 min; p < 0.05, respectively). Postoperative Pain at rest, and nausea and vomiting occurred with similar frequencies in the groups. Ketobemidone utilization in both infiltration groups, (2.4 +/- 1.8 mg and 3.1 +/- 1.8 mg, respectively) was not different compared to the IV fentanyl group (2.9 +/- 2.0 mg; NS). There were no differences in Postoperative antiemetic requirements during the first, second and third two-hour periods postoperatively. The dixyrazine consumption was similar in the three groups, (0.9 +/- 1.5 mg, 0.8 +/- 1.3 mg, and 1.4 +/- 1.8 mg, respectively; NS). Conclusion: Postsurgical ropivacaine wound infiltration, with or without adding fentanyl, demonstrates no differences in postoperative Pain relief and nausea/vomiting compared to a balanced general anesthetic including IV fentanyl. (C) 2003 by Elsevier Science Inc.
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- Nordin Fredrikson, Gunilla, et al.
(författare)
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Plasma oxidized LDL: a predictor for acute myocardial infarction?
- 2003
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Ingår i: Journal of Internal Medicine. - : Wiley. - 1365-2796 .- 0954-6820. ; 253:4, s. 425-429
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. Oxidized LDL has been attributed a key role in the development of atherosclerosis. Previous studies have demonstrated increased plasma levels of oxidized LDL in patients with established coronary artery disease. The aim of the present study was to investigate if plasma oxidized LDL also predicts risk for development of coronary heart disease (CHD). Design. We used a nested case-control design to study the association between plasma levels of oxidized LDL and risk for development of acute myocardial infarction (AMI) and/or death by CHD. Subjects. Oxidized LDL was analysed by ELISA in cases (n = 26), controls (n = 26) and controls with LDL cholesterol >5.0 mmol L-1 (n = 26). Results. Oxidized LDL correlated with total plasma and LDL cholesterol in both cases (r = 0.72, P < 0.01, r = 0.69, P < 0.01, respectively) and controls (r = 0.71, P < 0.01, r = 0.77, P < 0.01, respectively). The oxidized LDL/plasma cholesterol ratio was higher amongst cases (13.5, range 10.7-19.8) than in controls (12.6, range 9.5-15.8, P < 0.05) and hypercholesterolaemic controls (12.2, range 8.0-16.0, P < 0.01). Conclusions. These findings identify high plasma oxidized LDL/total cholesterol ratio as a possible indicator of increased risk for AMI.
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