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- Jonas, Örtegren, et al.
(författare)
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Cone motion viscosity and optical second harmonic generation of ferroelectric liquid crystalline dendrimers
- 2001
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Ingår i: Liquid crystals (Print). - : Informa UK Limited. - 0267-8292 .- 1366-5855. ; 28:6, s. 861-868
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Tidskriftsartikel (refereegranskat)abstract
- We report second harmonic generation in a ferroelectric liquid crystalline trimer and ferroelectric liquid crystalline dendrimers of first, second and third generation. Thin cells were filled with the compounds by capillary forces at elevated temperature, and cooled from the surface stabilized ferroelectric state to below the glass transition temperature, while kept in an electric field. The cone motion viscosity and the threshold electric field for unwinding of the helix axis of the chiral tilted smectic mesophases were studied separately at elevated temperature, and these data were used to optimize the preparation of the films. The measured response time was between 0.3 and 3 ms, which corresponds to a cone motion viscosity between 0.5 and 50 Pa s. Second harmonic generation was studied both at elevated temperature with an electric field and at room temperature with and without electric field. The first generation dendrimer exhibited a strong increase in the second order non-linear optical response with time at room temperature. The d(23)-coefficient of this dendrimer was approximately four times larger than for the other macromolecules and was 0.045 pm V-1. The relatively large d-coefficient of the first generation dendrimer is ascribed to crystallization, which improved the orientation of the molecular dipoles.
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- Ortegren, J., et al.
(författare)
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Improved thermal stability of pyroelectric polymers by crosslinking of ferroelectric liquid crystals
- 2001
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 105:42, s. 10223-10227
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Tidskriftsartikel (refereegranskat)abstract
- Monofunctional ferroelectric liquid crystalline monomers and a blend of monofunctional/lbifunctional ferroelectric liquid crystalline monomers were photopolymerized, yielding a side-chain liquid crystalline polymer and a cross-linked polymer, respectively. The cross-linked polymer exhibited higher thermal stability than the side-chain liquid crystalline polymer and was pyroelectric up to 170 degreesC, whereas the side-chain liquid crystalline polymer lost most of its pyroelectricity at 38 degreesC. It is shown by electrooptic and birefringence measurements that cross-linking in the unwound SmC* phase prevented the reoccurrence of the helical superstructure.
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- Ahlsén, Göran, et al.
(författare)
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Resistance profiles of cyclic and linear inhibitors of HIV-1 protease
- 2002
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Ingår i: Antiviral Chemistry & Chemotherapy. - 0956-3202 .- 2040-2066. ; 13:1, s. 27-37
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Tidskriftsartikel (refereegranskat)abstract
- Resistance to anti-HIV protease drugs is a major problem in the design of AIDS drugs with long-term efficacy. To identify structural features associated with a certain resistance profile, the inhibitory properties of a series of symmetric and asymmetric cyclic sulfamide, cyclic urea and linear transition-state analogue inhibitors of HIV-1 protease were investigated using wild-type and mutant enzyme. To allow a detailed structure-inhibition analysis, enzyme with single, double, triple and quadruple combinations of G48V, V82A, 184V and L90M substitutions was used. Kinetic analysis of the mutants revealed that catalytic efficiency was 1-30% of that for the wild-type enzyme, a consequence of reduced kcat in all cases and an increased KM for all mutants except for the G48V enzyme. The overall structure-inhibitory profiles of the cyclic compounds were similar, and the inhibition of the V82A, 184V and G48V/L90M mutants were less efficient than of the wild-type enzyme. The greatest increase in Ki was generally observed for the 184V mutant and least for the G48V/L90M mutant, and additional combinations of mutations did not result in improved inhibition profiles for the cyclic compounds. An extended analysis of additional mutants, and including a set of linear compounds, showed that the profile was unique for each compound, and did not reveal any general structural features associated with a certain inhibition profile. The effects of structural modifications in the inhibitors, or of mutations, were not additive and they differed depending on their context. The results demonstrate the difficulties in predicting resistance, even for closely related compounds, and designing compounds with improved resistance profiles.
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- Andersson, Anders, et al.
(författare)
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Hyperhomocysteinemia and changed plasma thiol redox status in chronic obstructive pulmonary disease
- 2001
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Ingår i: Clinical Chemistry and Laboratory Medicine. - 1434-6621. ; 39:3, s. 229-233
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Tidskriftsartikel (refereegranskat)abstract
- Reduced and total homocysteine, cysteine, glutathione and cysteinylglycine in plasma were investigated in 19 patients with chronic obstructive pulmonary disease and in 29 healthy subjects. The purpose was to examine the influence of pro-oxidant activity caused by the lung disease on the metabolism of homocysteine and other plasma thiols. We observed a decreased concentration of reduced glutathione and a decreased ratio of reduced/total glutathione in the patients compared to the healthy individuals, which supports the hypothesis of an association between free radicals and pathogenesis in some lung diseases. We also observed an increased total plasma homocysteine. The influence of a possible extracellular pro-oxidant activity on the concentration of total plasma homocysteine is discussed.
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- Andersson, Anders S, et al.
(författare)
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Vitamin supplementation normalizes total plasma homocysteine concentration but not plasma homocysteine redox status in patients with acute coronary syndromes and hyperhomocysteinemia.
- 2002
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Ingår i: Clinical Chemistry and Laboratory Medicine. - 1434-6621. ; 40:6, s. 554-558
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Tidskriftsartikel (refereegranskat)abstract
- Despite the growing evidence that elevated total homocysteine (tHcy) in plasma is a cardiovascular risk factor, the mechanism underlying the vascular injury is still unknown. Studies are difficult due to the fact that little is known about the formation of different homocysteine species in vivo. In the present study we have investigated the different fractions of tHcy in 21 patients with acute coronary syndromes and elevated concentration of plasma tHcy. A subgroup of the patients (n=16) was investigated before and after a 3 months study period with or without vitamin supplementation (folic acid 5 mg, pyridoxine 40 mg and cyanocobalamin 1 mg once daily). A major finding is that these patients had a lowered ratio (0.95%) between the concentration of reduced homocysteine (HcyH) and tHcy compared to controls (1.38%). A low ratio HcyH/tHcy in plasma in combination with elevated plasma tHcy concentrations might reflect increased oxidative activity or decreased reducing capacity in plasma from the patients. Another main finding in the present study is that, although vitamin supplementation of these patients normalized plasma tHcy, the ratio between HcyH and tHcy did not normalize. Since substantial evidence indicates that progression of arteriosclerosis is related to enhanced oxidant activity, the premature vascular disease associated with increased plasma tHcy concentration might be due to increased oxidative activity and the elevated plasma tHcy concentration may only reflect the increased oxidative stress.
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- Andersson, Claes, 1973, et al.
(författare)
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The urban economy as a scale-free network.
- 2003
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Ingår i: Physical Review E. - 2470-0045 .- 2470-0053. ; 68, s. 036124-
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Tidskriftsartikel (refereegranskat)abstract
- We present empirical evidence that land values are scale free and introduce a network model that reproduces the observations. The network approach to urban modeling is based on the assumption that the market dynamics that generates land values can be represented as a growing scale-free network. Our results suggest that the network properties of trade between specialized activities cause land values, and likely also other observables such as population, to be power-law distributed. In addition to being an attractive avenue for further analytical inquiry, the network representation is also applicable to empirical data and is thereby attractive for predictive modeling.
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- Andersson, Claes, 1973, et al.
(författare)
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The urban economy as a scale-free network
- 2003
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Ingår i: Physica A: Statistical Mechanics and its Applications. - 0378-4371. ; 345:1, s. 227-244
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Tidskriftsartikel (refereegranskat)abstract
- AbstractPower laws in socioeconomic systems are generally explained as being generated by multiplicative growth of aggregate objects. In this paper we formulate a model of geographic activity distribution with spatial correlations on the level of land lots where multiplicative growth is assumed to be dominant but not exclusive. The purpose is to retain the explanatory power of earlier models due to Simon, Gibrat and others while attaining some additional properties that are attractive for both empirical and modelling purposes. In this sense, the model presented here is a combination of the two factors that have been identified as central to urban evolution but rarely appear unified in the same model: transportation costs and multiplicative growth. The model is an elaboration of a previously reported complex network model of geographical land value evolution. We reproduce statistical properties of an empirical geographical distribution of land values on multiple hierarchical levels: land value per unit area, cluster areas, aggregated land value per cluster and cluster area/perimeter ratios. It is found that transportation effects are not strong enough to disturb the power law distribution of land values per unit area but strong enough to sort nodes to generate a new set of power laws on a higher level of aggregation. The main hypothesis is that all these relations can be understood as consequences of an underlying growing scale-free network of geographic economic interdependencies.
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| 10. |
- Appelros, Stefan, et al.
(författare)
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Short and long term outcome of severe acute pancreatitis.
- 2001
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Ingår i: European Journal of Surgery. - : Oxford University Press (OUP). - 1102-4151. ; 167:4, s. 281-286
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Between 1985 and 1994, 883 cases of acute pancreatitis were treated in Malmö, Sweden (population 233,000). The purpose of this study was to report the short- and long-term outcome of the 79 cases that were severe, according to the Atlanta classification. DESIGN: Retrospective and follow-up study a median time of 7 years since the attack. SETTING: University hospital, Sweden. SUBJECTS: 79 patients with severe acute pancreatitis. MAIN OUTCOME MEASURES: Mortality, cause of death, organ failure, local complications, surgical procedures, mortality since the attack, and endocrine and exocrine dysfunction. RESULTS: Twenty-one patients died from their attack. Organ failure was the predominant cause of death in the 13 patients who died during the first 10 days after admission, whereas infection was the most common cause of death in patients who died later. Mortality was low under the age of 60 and increased with age. Organ failure developed in 72 patients. Twenty-four patients developed pancreatic necrosis or abscesses and 18 patients were treated by necrosectomy and open or closed drainage. At follow-up, 13 patients had died, 2 from pancreatic carcinoma. 35 patients were included in the follow-up survey. 15 of these had diabetes and an additional 4 had impaired glucose tolerance. 9 patients had signs of severe exocrine dysfunction. CONCLUSIONS: There was a high incidence of endocrine and exocrine dysfunction together with, in many patients, ongoing social problems related to chronic alcoholism several years after an attack of severe acute pancreatitis.
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