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| 2. |
- Eriksson, Leif A., et al.
(författare)
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Symmetry breaking in charge-transfer compounds : The effects of electric fields and substituents on the properties of bipyrazine cations
- 1995
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Ingår i: Molecular Engineering. - 0925-5125 .- 1572-8951. ; 4:4, s. 339-352
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Tidskriftsartikel (refereegranskat)abstract
- The effects of an electric field and of various substituents on the symmetry breaking of degenerate near-midgap orbitals and on different properties in bi-N,N’-pyrazine-1,6-hexatriene dications ([C4N2H4—(CH)6—C4N2H4]2+) are investigated by means of semiempirical PM3 and INDO CI methods. The electric field is simulated by applying positive/negative point charges at varying distances from the end-points, and the substitutions are done with single chlorine atoms or with CN, OH or CH3 groups, at various positions along the chain or on one of the pyrazine rings. The results are compared with calculations on the unsubstituted, field-free system. It is found that an electric field (e.g., as applied over a membrane) leads to significant symmetry breaking and also polarizes the HOMO and LUMO, such that electron transfer between these orbitals generates large dipole-moment shifts and non-negligible oscillator strengths. With substituents, no major symmetry breaking is observed for the ground state. Instead, strong modifications of the orbital picture are observed, in particular when using the stronger electron-withdrawing substituents. Placing the substituent in a ring position does, furthermore, lead to the possibility of large charge transfer.
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| 5. |
- Eriksson, Leif, et al.
(författare)
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Cardiovascular effects of induced hypothermia after lung transplantation
- 1999
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Ingår i: Annals of Thoracic Surgery. - 1552-6259. ; 67:3, s. 804-809
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Induced hypothermia may be used to reduce metabolism in acute respiratory failure. Hypothermia is accompanied by an increase in pulmonary vascular resistance, as also seen in the early period after lung transplantation. It was our concern that the combination of the two would lead to an increased workload on the right ventricle. METHODS: To test this hypothesis we induced hypothermia to 32 degrees C in two groups of pigs. In one group we performed left single-lung transplantation combined with right pulmectomy (TRANSP group); in the other group, only right pulmectomy was performed (PULMEC group). RESULTS: During hypothermia, there was a significant increase in both groups in pulmonary vascular resistance (TRANSP group, 77%, p<0.05; PULMEC group, 54%, p<0.05) and a significant decrease in cardiac output (TRANSP group, 41%, p<0.05; PULMEC group, 34% p<0.05). Mean pulmonary artery pressure was unchanged, and the work done by the right ventricle was reduced (TRANSP group, 39%, p<0.05; PULMEC group, 31%). CONCLUSIONS: Induced hypothermia to 32 degrees C after lung transplantation resulted in a significant decrease in the work done by the right ventricle despite a significant increase in pulmonary vascular resistance.
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| 6. |
- Eriksson, Leif
(författare)
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Flocculation with Polyelectrolytes in Latex and Microbial Systems
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Adsorption of cationic polyelectrolytes onto polystyrene latices was studied as function of polymer chemical composition and molecular weight, polymer and surface charge density and ionic strength. The ratio between polymer charges and surface charges was close to one when distances between polymer and surface charges were equal. Overcompensation of the surface charge was obtained at higher polymer charge densities due to surplus of positive charges at the adsorption site and at lower polymer charge densities due to formation of loops and tails. Different lengths of side chains carrying the cationic groups had effects on the way the polymers neutralised the surface. Flocculation experiments under the same conditions as for the adsorption gave minima in floc size and strength when the distance between polymer and surface charges was the same. With reference to surface force measurements it was concluded that the polymers, depending on charge density, played several and different roles in capturing, binding and adhesion trough traditional bridging, electrostatic double layer bridging and electrostatic attraction. With low charge density polymers dominance of traditional bridging led to flexible and shear resistant flocs with dense structure on small length scales and a less dense fractal structure on larger length scales. With higher charge density increasing adhesion between the primary particles resulted in fractal structure on all length scales and decreasing shear resistance. This was compensated however with a god reflocculation ability. Different behaviour of flocs under and after high shear was related to shear history and to the degrees of traditional bridging and adhesion respectively. Separation properties of activated sludge bioflocs were related to the degree of crosslinking and shrinkage of the biopolymer matrix binding the bacterial cells together. This depended on the availability of calcium ions and on the energy input to the system. Flocculation of monocultured bacteria with polycations proceeded in two steps. First the anionic extracellular polymers from the bacteria were precipitated to polyelectrolyte complexes which on recharging flocculated the cells. Depending on the distribution of extracellular polymers between surface and liquid phase differently broad effective dosage ranges were obtained. For conditioning of sludges with large contents of biopolymers it was necessary with high charge density polycations and dosage need was mainly spent on polymer complexation as with the pure bacteria. For sludges with more particular character lower charge density polymers were advantaeous.
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| 7. |
- Eriksson, Leif, et al.
(författare)
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Induced hypothermia in critical respiratory failure after lung transplantation
- 1998
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Ingår i: Annals of Thoracic Surgery. - 1552-6259. ; 65:3, s. 827-829
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Tidskriftsartikel (refereegranskat)abstract
- Primary graft failure after lung transplantation is a serious complication with high mortality. We present 2 cases of critical respiratory failure after lung transplantation treated with surface cooling to 32 degrees and 35 degrees C, respectively, as an adjunct to conventional intensive care. Both patients were discharged from the hospital in good clinical condition. Surface cooling may be an effective mode of treatment in patients with critical respiratory failure after lung transplantation and should be considered before extracorporeal membrane oxygenation treatment is initiated.
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| 8. |
- Eriksson, Leif, et al.
(författare)
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Lung transplantation at the University of Lund 1990-1995. Analysis of the first 39 consecutive patients
- 1998
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Ingår i: Scandinavian Cardiovascular Journal. - : Informa UK Limited. - 1651-2006 .- 1401-7431. ; 32:1, s. 23-28
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Tidskriftsartikel (refereegranskat)abstract
- Between 1990 and 1995 39 patients were lung transplanted at the University Hospital in Lund. This is a retrospective review of survival and lung function in these patients. There were 17 single-lung transplants (SLT), 21 double-lung transplants (DLT) and 1 heart-lung transplant (HLT). Seven patients died during the period, giving an overall survival of 82%. One-year survival according to Kaplan-Meier survival analysis was 87%, and 2-year survival was 83%. Vital capacity and forced expiratory volume in 1 s (FEV1) 1 year after transplantation were 91% and 100% of predicted, respectively, in the DLT group and 60% and 50% in the SLT group. Bronchiolitis obliterans syndrome (BOS) developed in 11 of the 35 patients (31%) surviving more than 6 months, 2/21 in the DLT group and 8/13 in the SLT group and in the patient with HLT. The median time until detection of BOS was 11 months after the operation (range 6-18 months). Working capacity 1 year after transplantation was 60% of predicted in the DLT group and 47% of predicted in the SLT group. Ventilatory capacity was no longer function limiting. Lung transplantation today is a therapeutic option with a good medium-term survival and good functional results in selected patients with severe lung disease.
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| 9. |
- Eriksson, Leif
(författare)
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Lung Transplantation: Clinical and experimental studies
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the past 15 years lung transplantation has been established as a therapeutic option for patients with end-stage pulmonary disease. The results have improved over time and some transplantation centers now show 1-year survival rates above 80%. The number of donors has remained relatively constant during later years but the demand is increasing resulting in longer waiting times and an increasing number of patients dying on active waiting lists. Better lung preservation allowing longer cold ischemic times would potentially increase the donor pool and also improve immediate postoperative lung function. Paper I describes an experimental big animal model for evaluation of donor lungs in vivo. With this method we could show good preservation for 12 hours using a low-potassium-dextran-glucose solution (Perfadex). Another potential way of increasing the number of donors would be to accept organs from non-heart-beating donors i e dead from cardiac arrest. These donors will have died without systemic anticoagulation and will have been subjected to cardiopulmonary resuscitation with risk of traumatic injury to the lungs and aspiration. Paper III describes an ex vivo method for functional evaluation of donor lungs. There was good correlation between measurements of gas exchange in vivo and ex vivo. Paper II describes the physiological background for using gas exchange for CO2 in evaluating lung perfusion abnormalities. Acute graft failure represents a significant cause of early morbidity and mortality after lung transplantation, accounting for about 25% of all deaths in the first postoperative month. When conventional intensive care fails treatment options include re-transplantation and ECMO. Paper IV describes another approach, induced hypothermia to reduce metabolic needs, in the treatment of two patients in respiratory failure fulfilling established ECMO-criteria. Both patients could be stabilized and eventually discharged from the hospital with normal arterial blood gases. A finding in studies on hypothermia has been an increased pulmonary vascular resistance as is also seen early after lung transplantation. It was our concern that the combination of the two would prove detrimental to right ventricular function. The study presented in paper V did not show an increased work load on the right ventricle. Paper VI is a retrospective study of the first 39 lung transplantations performed in Lund between Jan 1990 and Dec 1995. Mean follow-up was 2.1 years. One-year survival was 87% and 2-year survival 83%. This compares favorably with other, larger transplant centers.
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| 10. |
- Llano, Jorge, et al.
(författare)
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Mechanism of Hydroxyl Radical Addition to Imidazole and Subsequent Water Elimination
- 1999
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 103:26, s. 5598-5607
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Tidskriftsartikel (refereegranskat)abstract
- The addition reaction of the hydroxyl radical to imidazole and subsequent elimination of water to form the 1-dehydroimidazolyl radical is investigated using MP2 and B3LYP methods, including large basis sets and SCI-PCM modeling of solvent effects. It is found that the barrier to addition of the hydroxyl radical at the 5-position is energetically favored over addition to the 2- or 4-positions by 2−3 kcal/mol at the SCI-PCM/MP2/6-311G(2df,p)//MP2/6-31G(d,p) level, whereas the corresponding B3LYP calculations yield a barrier-free addition at the 5-position. The lower barrier and NBO analysis explain the experimentally observed specificity for the 5-hydroxylation of imidazole and histidine, albeit the 2-adduct is about 4 kcal/mol more stable than the 5-adduct. The NBO energetic analysis shows that the exoanomeric effect stabilizes the transition state at the 5-position about 0.3 kcal/mol more than that at the 2-position. Moreover, the π-interaction between the attacking nonbonding spin orbital of the hydroxyl radical and the π-cloud of imidazole is the least for the transition state at the 5-position, favoring the σC5-O bond formation. The 5-hydroxyimidazolyl radical undergoes a slow elimination of water (the added OH group and the hydrogen at the N1 position) to yield the 1-dehydroimidazolyl radical. The base-catalyzed dehydration profile was modeled in two steps at the B3LYP/6-311G(2df,p)//6-31G(d,p) level. The PES for the dehydration reaction seems rather flat. The first step is a barrier-free loss of the proton at N1 induced by the hydroxide ion to yield the 1-dehydro-5-hydroxyimidazolyl radical anion. In the second step, the hydroxide ion is regenerated from the intermediate to yield the final product with a barrier of 2.7 kcal/mol. The calculated hyperfine structures in the presence of the continuum solvent model for the 5-hydroxyimidazolyl and 1-dehydroimidazolyl radicals are in close agreement with the experimental ones recorded in aqueous solution.
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