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- Korzhavyi, Pavel A., 1966-, et al.
(författare)
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Defect-induced magnetic structure in (Ga1-xMnx)As
- 2002
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 88:18, s. 187202-
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Tidskriftsartikel (refereegranskat)abstract
- We show that magnetic structures involving partial disorder of local magnetic moments on the Mn atoms in (Ga1-xMnx)As lower the total energy, compared to the case of perfect ferromagnetic ordering, when As defects on the Ga sublattice are present. Such magnetic structures are found to be stable for a range of concentrations of As antisites, and this result accounts for the observed magnetic moments and critical temperatures in (Ga1-xMnx)As . We propose an explanation for the stabilization of the partially disordered magnetic structures and conclude that the magnetization and critical temperatures should increase substantially by reducing the number of As antisite defects.
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- Andersson, A, et al.
(författare)
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Effect of nutrient enrichment on the distribution and sedimentation of polychlorinated biphenyls (PCBs) in seawater
- 1998
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Ingår i: Hydrobiologia. - 0018-8158 .- 1573-5117. ; 377, s. 45-56
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Tidskriftsartikel (refereegranskat)abstract
- The effect of nutrient enrichment on the distribution of polychlorinated biphenyl's (PCBs) in the microbial food web and the residence time of PCBs in seawater was studied in an experimental mesocosm system. Two 5 m high temperature and light controlled mesocosm tubes (empty set = 0.5 m) were filled with seawater from the northern Baltic Sea. Inorganic phosphorus and nitrogen were added daily to one mesocosm, while the other served as a control. Experiments were conducted at 5, 10 and 20 degrees C. Three C-14-labelled PCBs of different degree of chlorination were added to subsamples of the mesocosms: 4-chlorobiphenyl (MCB), IUPAC # 3, 2,2',5,5'-tetrachlorobiphenyl (TCB), IUPAC # 52 and 2,2',4,4',5,5'-hexachlorobiphenyl (HCB) IUPAC # 153. The biomasses and growth rates of the microorganisms as well as the sedimentation rate of particulate organic material increased with nutrient enrichment. The size distribution of the microorganisms changed with nutrient status, from dominance of picoplankton (< 2 mu m) in the control towards increased importance of micro (> 10 mu m) and nanoplankton (2-10 mu m) in nutrient enrichment. The specific growth rate of the bacterial community was found to be more temperature dependent than that of the phytoplankton community. The relative proportion of PCBs in the > 2 mu m fraction was observed to be in the order MCB < TCB < HCB, while the opposite distribution prevailed in the < 2 mu m fraction. We hypothesize that this is due to the combined effect of the different K-ow values of the PCBs and a different composition of the particulate organic carbon in the > 2 mu m and < 2 mu m fractions (e.g. different lipid composition). The residence time of the PCBs in the mesocosm generally decreased with nutrient enrichment, but was dependent on the degree of chlorination of the PCB. Our results indicate that the transport of organic pollutants up through the food web is more important in nutrient poor than in nutrient rich waters and that the importance of sedimentation is higher in eutrophic ecosystems.
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- Belch, Jill J. F., et al.
(författare)
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Results of the randomized, placebo-controlled clopidogrel and acetylsalicylic acid in bypass surgery for peripheral arterial disease (CASPAR) trial
- 2010
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Ingår i: Journal of vascular surgery : official publication, the Society for Vascular Surgery [and] International Society for Cardiovascular Surgery, North American Chapter. - : Elsevier BV. - 0741-5214. ; 52:4, s. 825-833, 833.e1-2
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Tidskriftsartikel (refereegranskat)abstract
- The combination of clopidogrel plus ASA did not improve limb or systemic outcomes in the overall population of PAD patients requiring below-knee bypass grafting. Subgroup analysis suggests that clopidogrel plus ASA confers benefit in patients receiving prosthetic grafts without significantly increasing major bleeding risk.
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- Bergqvist, David, et al.
(författare)
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Prolonged prophylaxis against venous thromboembolism with enoxaparin in patients undergoing cancer surgery : long-term survival analysis
- 2006
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Ingår i: Phlebology. - : SAGE Publications. - 0268-3555 .- 1758-1125. ; 21:4, s. 195-198
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Tidskriftsartikel (refereegranskat)abstract
- Objective: ENOXACAN II was a randomized, double-blind trial that showed prolonged (four-week) thromboprophylaxis with enoxaparin to be more effective than and as safe as standard (one-week) thromboprophylaxis in patients undergoing surgery with a curative intent for abdominopelvic cancer. This follow-up study compared long-term, all-cause mortality in both groups. Methods: Survival rates were calculated on the randomized, treated population (n = 501). The primary efficacy endpoint was survival at one year. An exploratory analysis including survival data up to 44 months was performed. Because some patients were deemed to have undergone palliative as opposed to curative surgery, and there was a significant difference between the treatment groups in the percentage of patients undergoing palliative surgery, the survival analyses were adjusted for the type of surgery performed. Results: When adjusted for type of surgery, there was a trend towards reduced mortality among patients undergoing palliative surgery in the prolonged prophylaxis group (hazard ratio [HR] = 0.598, P = 0.3565) that became more pronounced beyond the pre-specified one-year follow-up period (HR = 0.469, P = 0.078). This trend may reflect a beneficial effect of prolonged prophylaxis on survival in the palliative surgery group (one-year survival 65.4 versus 50% for standard prophylaxis). In patients undergoing curative surgery, one-year survival rates were equal in the standard and prolonged prophylaxis groups (93.8 and 93.2%, respectively). Conclusion: Prolonged thromboprophylaxis with enoxaparin may affect long-term survival in palliative surgery for cancer, but further investigation is warranted.
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- Bergqvist, Lars, 1976-, et al.
(författare)
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Magnetic and electronic structure of (Ga1-xMnx)As
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:20, s. 205201-
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Tidskriftsartikel (refereegranskat)abstract
- We present theoretical calculations of the magnetic and electronic structure of Mn-doped GaAs (in the zinc-blende structure). The magnetic properties are shown to be very sensitive to structural defects, in particular, As antisite defects and Mn at interstitial positions. Only when considering such defects can the experimental magnetic moments be reproduced by first-principles theory. We present a simple model for understanding the connection between the magnetic ordering and the As antisites, and the way in which the defects help to stabilize a partial disordered local-moment state. The connection between the energetics of the Mn substitution and the As antisite concentration is also analyzed. In addition, we compare the calculated magnetic properties and electronic structures of Mn situated on substitutional sites (Mn replacing a Ga atom) and on interstitial sites, where in agreement with observations the interstitial site is found to be less favorable. Finally, combining our first-principles calculations of the spin-wave excitation energies with a classical Heisenberg Hamiltonian we have calculated interatomic exchange interactions, and using Monte Carlo simulations we present theoretical values of the critical temperature as a function of Mn concentration.
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