| 1. |
- Hedlund, J., et al.
(författare)
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Management of patients with community-acquired pneumonia treated in hospital in Sweden
- 2002
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Ingår i: Scandinavian Journal of Infectious Diseases. - 0036-5548. ; 34:12, s. 887-92
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the management of patients with community-acquired pneumonia (CAP) treated in hospital in Sweden, a multicentre retrospective cohort study was performed with medical record review of 982 patients (mean age 63 y) at 17 departments of infectious diseases at hospitals in Sweden. Information on antimicrobial therapy, demographic characteristics, comorbid conditions, physical examination findings, and laboratory and microbiological test results were recorded. Outcome measures were in-hospital mortality and length of hospital stay (LOS). Cultures were obtained from blood in 80% and from sputum in 22% of the patients. A microbiological aetiology was determined for 23% of the patients, with Streptococcus pneumoniae as the dominating agent (9%). The initial antibiotic treatment was mostly given intravenously (78%). Penicillin (50%) or a cephalosporin (30%) was the most common choice. Both of these drugs were usually given as a single agent. The overall mortality was 3.5% and the mean LOS was 6.4 d. Thus, the outcome was favourable despite the empirical antibiotic treatment having a narrow spectrum compared with the broader approach recommended in most recent guidelines on the management of CAP. These findings suggest that a majority of patients who are hospitalized with moderately severe pneumonia can be treated initially with penicillin alone.
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| 2. |
- Uhnoo, I., et al.
(författare)
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Treatment and prevention of influenza : Swedish recommendations
- 2003
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Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 35:1
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Tidskriftsartikel (refereegranskat)abstract
- The introduction of the 2 neuraminidase inhibitors (NAIs) zanamivir and oseltamivir has offered new options for the prevention and treatment of influenza. This article summarizes a Swedish consensus guidance document on the rational use of antiviral drugs in the management of influenza virus infections. Vaccination remains the cornerstone for influenza prophylaxis. Target groups for the annual vaccination programme are the 'at-risk' individuals, i.e. elderly patients (= 65 y) and patients with chronic pulmonary disease or cardiovascular disease or other chronic diseases predisposing for a complicated course of influenza. Antiviral drugs are not a substitute for influenza vaccination, but could be used as adjuncts. Currently, 3 drugs have been approved for the treatment of influenza, including zanamivir and oseltamivir and the M2 inhibitor amantadin. Amantadin has come to very limited use, has recently been withdrawn from the Swedish market and is available only on a named patient basis. Compared with amantadin, the NAIs have clear advantages because of their broader anti-influenza activity against both type A and B, improved safety profiles and low potential for inducing drug resistance. The NAIs are therefore recommended as first options in the treatment of influenza. Oseltamivir can be taken orally, whereas zanamivir is for oral inhalation. Limited in vitro and in vivo data suggest that oseltamivir is less potent against influenza B, whereas zanamivir seems equally effective against influenza A and B. In influenza-positive healthy adults and children, treated within 48 h after symptom onset, the NAIs shorten the duration of illness by about 1 d. No significant effect on the duration of symptoms has been documented in treated at-risk patients with influenza. Owing to their limited therapeutic benefit, general use of the NAIs in the treatment of influenza is not recommended, but they can be advocated on an individualized basis for patients with severe influenza who can start therapy within 48 h of the onset of symptoms. Zanamivir is the preferred choice in a confirmed influenza B epidemic. For prevention of influenza, 2 drugs are approved, oseltamivir in adults above 12 y old and amantadin in people above 10 y old. The 70-90% protective efficacy of oseltamivir for household postexposure prophylaxis and for seasonal prophylaxis is comparable to that reported for amantadin. Oseltamivir is the preferred drug for prophylactic use. Chemoprophylaxis is targeted at high-risk groups and should be considered on a case-by-case basis depending on the circumstances and the population requiring protection. A broader preventive use of oseltamivir can be advocated in at-risk groups during seasons when there is a poor antigenic match between the epidemic strains and the vaccine strains. Oseltamivir prophylaxis is otherwise recommended for patients unable to be vaccinated and for families exposed to influenza which include a member of the at-risk groups. In high-risk hospital units and in institutions caring for the elderly, oseltamivir prophylaxis, in combination with vaccination, can be recommended as measures to control an influenza outbreak.
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| 3. |
- Claesson, A., et al.
(författare)
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Diode-pumped miniature lasers using microstructured silicon carriers
- 2000
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 0013-5194 .- 1350-911X. ; 36:5, s. 433-434
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Tidskriftsartikel (refereegranskat)abstract
- A new versatile design concept for compact diode-pumped solid-state lasers based on a microstructured silicon carrier with etched V-grooves is presented. The carrier provides efficient thermal management as well as compact integration and alignment of all active acid passive optical components. In initial experiments, an Nd:YAG laser delivered a continuous-wave output of 3W.
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| 4. |
- Lagergren, K, et al.
(författare)
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Evidence for excited states in Ag-95
- 2002
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Ingår i: European Physical Journal A. - : Springer. - 1434-6001 .- 1434-601X. ; 14:4, s. 393-396
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Tidskriftsartikel (refereegranskat)abstract
- The first evidence for excited states in Ag-95 is presented. Ag-95 is the heaviest T-z = 1/2 nucleus for which gamma-rays have been identified. The reaction Ca-40(Ni-58, 1p2n)Ag-95 was used in the experiment, which resulted in the assignment of three gamma-rays to Ag-95. A detector system consisting of the detector arrays Euroball, Neutron Wall and Euclides was used to detect gamma-rays, neutrons and charged particles, respectively.
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| 5. |
- Abraham, T., et al.
(författare)
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Polyelectrolyte-mediated interaction between similarly charged surfaces : Role of divalent counter ions in tuning surface forces
- 2001
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 17:26, s. 8321-8327
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Tidskriftsartikel (refereegranskat)abstract
- The effects of divalent salts (CaCl2, MgCl2 and BaCl2) in promoting the adsorption of weakly charged polyelectrolyte (polyacrylic acid), PAA, Mw similar to 250000 g/mol) on mica surfaces and their role in tuning the nature of interactions between such adsorbed polyelectrolyte layers were studied using the interferometric surface forces apparatus. With mica surfaces in 3 mM MgCl2 solutions at pH similar to8.0-9.0, the addition of 10 ppm PAA resulted in a long-range attractive bridging force and a short-range repulsive steric force. This force profile indicates a low surface coverage and weak adsorption. The range of the force can be related to the characteristic length scale R-G of polyelectrolyte chains using a scaling description. An increase of the PAA concentration to 50 ppm changed the attractive force profile to a monotonic, long-range repulsive interaction extending up to 600 Angstrom due to the increased surface coverage of polyelectrolyte chains on the mica surfaces. Comparison of the measured forces with a scaling mean field model suggests that the adsorbed polyelectrolyte chains are stretched, which eventually give rise to the polyelectrolyte brush like structure. When the mica surfaces were preincubated in 3 mM CaCl2 at pH similar to8.0-9.0, in contrast to the case of 3 MM MgCl2, the addition of 10 ppm PAA resulted in a more complex force profile: long-range repulsive forces extending up to 800 Angstrom followed by an attractive force regime and a second repulsive force regime at shorter separations. The long-range electrosteric forces can be attributed to strong adsorption of polyelectrolyte chains on mica surfaces (high surface coverage) which is facilitated by the presence of Ca2+ ions, while the intermediate range attractive forces can be ascribed to Ca2+ assisted bridging between adsorbed polyelectrolyte chains. Also interesting is to note various relaxation processes present in this system. In contrast to both MgCl2 and CaCl2 systems, with mica surfaces in 3 mM BaCl2 solution at pH similar to8.0-9.0, the addition of 10 ppm PAA resulted in precipitation of polyelectrolyte chains on mica surfaces, resulting in an extremely long-range monotonic repulsive force profile. In summary, our study showed that divalent counterions (Mg2+, Ca2+, and Ba2+) exhibit significantly different behavior in promoting PAA adsorption on mica surfaces, modifying and controlling various surface interactions.
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| 6. |
- Al-Otaibi, M, et al.
(författare)
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Subgingival plaque microbiota in Saudi Arabians after use of miswak chewing stick and toothbrush
- 2004
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Ingår i: Journal of Clinical Periodontology. - 0303-6979 .- 1600-051X. ; 31:12, s. 1048-53
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The chewing stick, the miswak, is used in many developing countries as the traditional means for oral hygiene. It is prepared from the roots, twigs and stem of Salvadora persica or other alternative local plants. OBJECTIVES: To compare the effects of the chewing stick miswak (from S. persica) and toothbrush on subgingival plaque microflora among Saudi Arabian individuals. Further, to investigate whether components extracted from S. persica may interfere with the subgingival plaque micro-organisms. MATERIAL AND METHODS: Fifteen healthy Saudi Arabian male volunteers aged 21-36 years were included in a single-blind, randomized cross-over study. The participants were taught how to use each device properly. Plaque sampling for DNA test was performed at the baseline, 1 week after professional tooth cleaning, and after 3 weeks of either miswak or toothbrush use. Identification and quantification of microbial species were performed by the checkerboard method, using whole genomic, digoxigenin-labelled DNA probes. Inhibition zones around miswak were examined on agar plates with Actinobacillus actinomycetemcomitans and the leukotoxicity of this bacterium was analyzed in a bioassay with macrophages+/-extracts of miswak. RESULTS: Miswak and toothbrushing had a similar influence on the levels of the subgingival microbiota. However, A. actinomycetemcomitans was significantly more reduced by miswak (p<0.05) than by toothbrushing. These results were supported by our in vitro results which, indicated that extracts from S. persica might interfere with the growth and leukotoxicity of A. actinomycetemcomitans. CONCLUSIONS: In contrast to toothbrush use, miswak use significantly reduced the amount of A. actinomycetemcomitans in the subgingival plaque.
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| 7. |
- Bränden, Petter, et al.
(författare)
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Catalan continued fractions, and increasing subsequences in permutations
- 2002
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Ingår i: Discrete Mathematics. - 0012-365X .- 1872-681X. ; 258:03-jan, s. 275-287
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Tidskriftsartikel (refereegranskat)abstract
- We call a Stieltjes continued fraction with monic monomial numerators a Catalan continued fraction. Let e(k)(pi) be the number of increasing subsequences of length k + 1 in the permutation pi. We prove that any Catalan continued fraction is the multivariate generating function of a family of statistics on the 132-avoiding permutations, each consisting of a (possibly infinite) linear combination of the e(k)S. Moreover, there is an invertible linear transformation that translates between linear combinations of ekS and the corresponding continued fractions. Some applications are given, one of which relates fountains of coins to 132-avoiding permutations according to number of inversions. Another relates ballot numbers to such permutations according to number of right-to-left maxima.
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| 8. |
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| 9. |
- Claesson, Hans, et al.
(författare)
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Rheological behaviour during UV-curing of a star-branched polyester
- 2002
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Ingår i: Progress in organic coatings. - 0300-9440 .- 1873-331X. ; 44:1, s. 63-67
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Tidskriftsartikel (refereegranskat)abstract
- Using a rheometer coupled with an UV-light generator, the viscoelastic behaviour during the fast cure of star-branched polyester is investigated. The 32 arm star polymers consist of a hyperbranched polyester core, Boltorn(TM) and linear grafts of poly(E-caprolactone) (degree of polymerisation: 20-52) with methacrylate end groups. The resins are crystalline and the melting points range from 34 to 50degreesC; films can be formed and cured below 80degreesC. The crossover of G' and G was used as the gel point. The time to reach the gel point, a few seconds, increases linearly with molecular weight.
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- Claesson, Åsa, et al.
(författare)
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Internal Electrode Fiber Polarization Controller
- 2003
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Ingår i: Conf Opt Fiber Commun Tech Dig Ser. ; , s. 39-40
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Konferensbidrag (refereegranskat)abstract
- Potentially low-cost polarization controllers were studied with a current-driven internal electrode fibers. The return loss was determined for the device. An EDFA was used as light source, and five devices were constructed and tested. The polarization dependent loss (PDL) of the polarization controllers was measured between 1530 nm and 1570 nm using the Jones-matrix method. The response times for the controllers was found to be relatively slow. The rise time of the optical response was significantly improved by overshooting the current pulse.
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| 14. |
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| 15. |
- Dedinaite, A, et al.
(författare)
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Interactions between surfaces coated with cationic hydrophobically modified polyelectrolyte in the presence and the absence of oppositely charged surfactant
- 2000
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 116, s. 84-94
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Tidskriftsartikel (refereegranskat)abstract
- (1) Department of Chemistry Surface Chemistry Royal Institute of Technology 100 44 Stockholm and Institute for Surface Chemistry, Box 5607, 114 86 Stockholm Sweden (2) Laboratoire de Physico-Chimie Macromoleculaire, UMR-7615, ESPCI CNRS, Universite Pierre et Marie Curie ESPCI, 10 Rue Vauquelin, 75231 Paris Cedex 5, France The association between a cationic hydrophobically modified polyelectrolyte and an anionic surfactant was investigated in bulk solution and at a negatively charged solid surface. The bulk association was followed by measurements of turbidity and electrophoretic mobility. The maximum turbidity of the solution was found to closely coincide with the point of zero electrophoretic mobility of the aggregates. The forces acting between negatively charged mica surfaces across a dilute aqueous solution of the hydrophobically modified polyelectrolyte were monitored using surface force measurements. The presence of hydrophobic side chains on the polyelectrolyte leads to adsorption in an inner rather compact layer and an outer extended layer. After dilution only the inner layer remains adsorbed to the surface. In the next step, sodium dodecyl sulphate (SDS) was added. It was found that the anionic surfactant is incorporated in the adsorbed layer even at very low bulk concentrations. As the surfactant concentration is increased stepwise the layer first swells and relaxes very slowly during compression. At higher SDS concentrations, desorption occurs. The interfacial properties of the hydrophobically modified polyelectrolyte alone and in mixtures with SDS are in many ways strikingly different to those of non-hydrophobically modified polyelectrolytes having a similar linear charge density. This is due to the importance of hydrophobic interactions between the hydrophobic side chains of the polyelectrolyte and between these groups and the nonpolar part of the surfactant
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| 16. |
- Dedinaite, A, et al.
(författare)
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Interfacial properties of aggregates formed by cationic polyelectrolyte and anionic surfactant
- 2000
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 16, s. 1951-1959
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Tidskriftsartikel (refereegranskat)abstract
- Interactions between mica surfaces across aqueous solutions containing mixtures of a highly positively charged polyelectrolyte and an anionic surfactant were studied using a surface force apparatus. The investigation was carried out using a constant polyelectrolyte concentration (20 ppm) and a wide range of surfactant concentrations (0 - 1 cmc). The chemical composition of the adsorbed polyelectrolyte-surfactant layers was analysed by XPS. The properties of polyelectrolyte-surfactant aggregates formed in bulk were studied by measurements of turbidity and electrophoretic mobility. The aggregates formed at low surfactant concentrations (<0.04 cmc) were positively charged, whereas at higher surfactant concentrations the aggregates carried a net negative charge. It was shown that polyelectrolyte-surfactant aggregates rapidly adsorb on negatively charged mica surfaces regardless of the sign of their charge. At surfactant concentrations up to 0.01 cmc, the polyelectrolytes adsorb on mica surfaces with loops and tails stretching out into solution and repulsive steric forces are generated. The thickness of the layer decreases with time and we suggest that this conformational change is accompanied by some expulsion of surfactant >from the adsorbed layers. Thick adsorbed layers were formed in the surfactant concentration range 0.02 - 0.1 cmc. In this concentration regime the measurement of equilibrium forces was inaccessible due to a very slow layer relaxation. During compression the forces were repulsive and during separation an attraction developed. We attribute this to formation of interlayer surfactant bridges. Finally, at high surfactant concentrations (≥ 0.4 cmc) highly negatively charged aggregates adsorb on the surfaces in rather thin layers, resulting in purely repulsive forces of mixed electrostatic and steric origin.
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| 17. |
- Dedinaite, A, et al.
(författare)
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Polyelectrolyte-surfactant layers: Adsorption of preformed aggregates versus adsorption of surfactant to preadsorbed polyelectrolyte
- 2000
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 16, s. 5257-5266
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Tidskriftsartikel (refereegranskat)abstract
- The character of adsorbed layers containing both polyelectrolyte and surfactant depends on the type of polyelectrolyte used and the surfactant concentrations, as demonstrated by several recent studies. However, the layer properties also depend on the experimental pathway. This shows that the adsorbed layers can be trapped in quasi-equilibrium states, and that the true equilibrium state is only reached over experimentally inaccessible time scales. This has to be kept in mind when comparing different results reported in the literature. The present article highlights these effects using a system consisting of a highly charged cationic polyelectrolyte and an anionic surfactant. The adsorbed layer properties were determined using mainly surface force measurements and AFM imaging. We also present some new small angle neutron scattering data for bulk complexes formed between the polyelectrolyte and the surfactant, which demonstrates the presence of a characteristic correlation length of about 37-39 Å. A similar characteristic length-scale is also observed in some of the adsorbed layers, both employing the AFM and the surface force apparatus.
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| 18. |
- Ekholm, P., et al.
(författare)
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A quartz crystal microbalance study of the adsorption of asphaltenes and resins onto a hydrophilic surface
- 2002
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 247:2, s. 342-350
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of extracted and purified samples of asphaltenes and resins onto gold surfaces has been studied as a function of bulk concentration using a quarts crystal microbalance with dissipation measurements (QCM-D). With this device, which works equally well in transparent, opaque, and nontransparent samples, the adsorbed amount is measured through a change in resonant frequency of the quartz oscillator. The measured change in dissipation reports on changes in layer viscoelasticity and slip of the solvent at the surface. The results show that the adsorbed amount for resins from heptane corresponds to a rigidly attached monolayer. The adsorbed amount decreases with increasing amount of toluene in the solvent and is virtually zero in pure toluene. Asphaltenes, on the other hand, adsorb in large quantities and the mass and dissipation data demonstrate the presence of aggregates on the surface. The aggregates are firmly attached and cannot be removed by addition of resins. On the other hand, resins and asphaltenes associate in bulk liquid and the adsorption from mixtures containing both resins and asphaltenes is markedly different from that obtained from the pure components. Hence, we conclude that preformed resin aggregates adsorb to the surface. These results are compared and discussed in relation to adsorption from crude oil diluted in heptane/toluene mixtures.
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| 19. |
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| 20. |
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Osterberg, M., et al.
(författare)
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Forces between xylan-coated surfaces : Effect of polymer charge density and background electrolyte
- 2001
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 242:1, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- The forces between xylan-coated mica surfaces at pH 10 have been studied using the interferometric surface force apparatus. Xylan is a polysaccharide that is composed of (1,4)-linked beta -D-xylopyranose units, which are partially substituted at C2 with 4-O-methyl-alpha -D-glucuronic acid units and at C3 with alpha -L-arabinosyl units. Two different xylans were studied, one with 0.5% and one with 9% of the segments containing a carboxylic acid group. It was found that both xylans adsorbed onto the negatively charged mica surface despite their negative charge. The interactions between the xylan-coated surfaces were dependent on the charge density of the polymer. The xylan with higher charge density adsorbed in a more extended conformation leading to more long-range repulsion. The shapes of the force curves were consistent with the forces expected for anchored polyelectrolyte brushes. After compression the length of the protruding chains decreased. An increase in background electrolyte concentration led to a decrease in the range of the repulsion. This effect was, as expected, more pronounced for the high charge density xylan. In the presence of CaCl2 not only the long-range forces but also the layer thickness at high compressive load decreased.
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| 27. |
- Plunkett, M. A., et al.
(författare)
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Adsorption of a cationic polyelectrolyte followed by surfactant-induced swelling, studied with a quartz crystal microbalance
- 2002
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 18:4, s. 1274-1280
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption and subsequent surfactant-induced swelling of a 10% charged cationic polyelectrolyte (AM-MAPTAC-10), on a gold surface, was monitored by means of a quartz crystal microbalance with dissipation (QCM-D). This instrument gives information on the total adsorbed amount including any adsorbed solvent and on the manner of adsorption. In this case the total adsorbed amount from a 20 ppm AM-MAPTAC-10 solution registered by the QCM-D device was approximately 0.6 mug cm(-2). X-ray photoelectron spectroscopy results showed that the polyelectrolyte adsorbed mass was 0.16 mug cm(-2); thus the water trapped within the polyelectrolyte layer constitutes about 70% of the mass measured by the quartz crystal microbalance. The adsorption process was found to be rather complex, though the time evolution of the adsorbed mass indicated that the majority of the process was diffusion controlled, Toward the end of the adsorption process, the rate of adsorption drops off and the dissipation rate increases, indicating that as the surface becomes crowded the layer extends further in the direction normal to the surface. The effect of addition of sodium dodecyl sulfate (SIDS) to a preadsorped AM-MAPTAC-10 layer was also investigated. It was found that some swelling of the preadsorbed layer occurred once the bulk surfactant concentration reached 20% of the critical micelle concentration (cmc). Between 60% of the cmc and twice the cmc, the adsorbed layer swelled significantly and desorption started to occur. Rinsing the surface with the surfactant-free electrolyte solution results in a rapid decrease in dissipation and adsorbed mass indicating the removal of the surfactant but not the polyelectrolyte.
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| 28. |
- Plunkett, M. A., et al.
(författare)
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Comparison of the adsorption of different charge density polyelectrolytes : A quartz crystal microbalance and X-ray photoelectron spectroscopy study
- 2003
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 19:11, s. 4673-4681
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of a series of six cationic polyelectrolytes onto a gold surface was monitored via a quartz crystal microbalance with dissipation (QCM-D). The series of polyelectrolytes were chemically similar but differing in the ratio of two randomly ordered constituent monomers, one of which was charged, the other neutral. Thus the series of polyelectrolytes differed systematically in their charge densities, ranging from a high charge density (100% of monomers charged) to a low charge density (1% charged). It was determined that high charge density polyelectrolytes adsorbed in a relatively flat and rigid layer, while the low charge density polyelectrolyte, as expected, adsorbed in a much more extended structure that coupled strongly to the bulk solvent. By comparison to X-ray photoelectron spectroscopy results, we have also calculated the relative solvent mass hydrodynamically coupled to the adsorbed polymer, which ranges from almost 80% solvent for the 1% charged case down to close to zero for the 100% charged case. Since the QCM-D results are measured relative to uncoated gold in aqueous solution, the latter results should be interpreted as showing that the amount of water hydrodynamically coupled to gold and that coupled to gold coated with the 100% charged polyelectrolyte is very similar. It is believed that this systematic study on the effect of polyelectrolyte structure on the measured dissipation change in the QCM-D may serve as a first guide when inferring structural and viscoelastic information based solely on the QCM-D technique for other similar systems. In addition, a preliminary study on the ability of one polymer to replace another preadsorbed polymer layer was conducted that showed that a steric layer was able to prevent the adsorption of a thermodynamically more favorable polymer. In the reverse case, greater exchange was possible.
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| 29. |
- Poptoshev, E, et al.
(författare)
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Comparison of model surfaces for cellulose interactions; elevated pH
- 2000
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 116, s. 79-83
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Tidskriftsartikel (refereegranskat)abstract
- Two different substrates have been used to measure interaction forces between cellulose and between cellulose and glass at normal and high pH. Forces between microspheres of cellulose (r=20-30 µm) have been measured using the colloidal probe atomic force microscopy technique. Interactions between Langmuir-Blodgett cellulose films on a hydrophobised mica substrate and a glass sphere have been determined with the noninterferometric surface force apparatus. Also, the interaction between two identical Langmuir-Blodgett cellulose films determined with the interferometric surface force apparatus is given for comparison. At low pH (5.5-6) the interaction at large separations in both systems is characterised by a double-layer repulsion with an electrosteric contribution dominating the shorter-range regime. At pH 10, the Langmuir-Blodgett cellulose film swells considerably, which generates a long-range steric repulsion. In many cases several inward steps have been observed in the force-distance curves. We attribute this to a sudden partial collapse of the swollen cellulose film. After initial compression of the steric layer (upon consecutive force runs) the long-range interaction is again dominated by a double-layer force. In contrast, measurements between two cellulose spheres have shown no excessive swelling. Only a limited increase (from about 10 nm to about 20 nm per surface) of the range of the electrosteric repulsion has been found at pH 10. The force at longer distances is in good agreement with the Poisson-Boltzmann theory, with the surface potential increasing with pH as expected.
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| 30. |
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| 31. |
- Rippner Blomqvist, Brita, et al.
(författare)
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Disruption of viscoelastic beta-lactoglobulin surface layers at the air-water interface by nonionic polymeric surfactants
- 2004
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:23, s. 10150-10158
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Tidskriftsartikel (refereegranskat)abstract
- Nonequilibrium interfacial layers formed by competitive adsorption of beta-lactoglobulin and the nonionic triblock copolymer PEO99-PPO65-PEO99 (F127) to the air-water interface were investigated in order to explain the influence of polymeric surfactants on protein film surface rheology and foam stability. Surface dilatational and shear rheological methods, surface tension measurements, dynamic thin-film measurements, diffusion measurements (from fluorescence recovery after photo bleaching), and determinations of foam stability were used as methods. The high surface viscoelasticity, both the shear and dilatational, of the protein films was significantly reduced by coadsorption of polymeric surfactant. The drainage rate of single thin films, in the presence of P-lactoglobulin, increased with the amount of added F 127, but equilibrium F127 films were found to be thicker than beta-lactoglobulin films, even at low concentration of the polymeric surfactant. It is concluded that the effect of the nonionic triblock copolymer on the interfacial rheology of beta-lactoglobulin layers is similar to that of low molecular weight surfactants. They differ however in that F127 increases the thickness of thin liquid films. In addition, the significant destabilizing effect of low molecular weight surfactants on protein foams is not found in the investigated system. This is explained as due to long-range steric forces starting to stabilize the foam films at low concentrations of F127.
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| 32. |
- Sandberg, Mats, et al.
(författare)
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Urban Morphology and windiness
- 2004
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Ingår i: Cost Action C14 Impact of Wind and Storm on City Life and Built Environment May 5-7. - 2930389117
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 33. |
- Silvander, M., et al.
(författare)
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Rheological properties of phospholipid-stabilized parenteral oil-in-water emulsions - effects of electrolyte concentration and presence of heparin
- 2003
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Ingår i: International Journal of Pharmaceutics. - 0378-5173 .- 1873-3476. ; 252:02-jan, s. 123-132
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Tidskriftsartikel (refereegranskat)abstract
- The rheological properties of the parenteral oil-in-water emulsion Intralipid(TM) were investigated. The viscosity data at different phase volumes correlated well with that obtained via a theoretical model developed by Yaron and Gal-Or. The model also describes the temperature dependence well. The effects of electrolyte addition were also investigated. Monovalent sodium chloride had practically no influence on viscosity. Calcium chloride, on the other hand, had a large impact on viscosity even at low concentrations. It was shown that the obtained maximum in viscosity coincided with the zeta-potential being close to zero. The resulting increase in viscosity is due to flocculation that leads to an increase in apparent phase volume. A similar behaviour was obtained with magnesium chloride with the difference that the maximum in viscosity was shifted to higher electrolyte concentrations. This is interpreted as that because magnesium binds strongly to the hydration water than does calcium. The addition of the negatively charged anti-coagulant heparin causes flocculation in the presence of small amounts of calcium. The amounts of calcium needed for such bridging flocculation is lower than what is needed in order to create a positive potential at the surfaces of the droplets. A fraction of the floes is not broken down even by extensive shear.
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| 34. |
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| 35. |
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| 36. |
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| 37. |
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