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| 4. |
- Christenson, H. K., et al.
(författare)
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Direct measurements of the force between hydrophobic surfaces in water
- 2001
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Ingår i: Advances in Colloid and Interface Science. - 0001-8686 .- 1873-3727. ; 91:3, s. 391-436
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Forskningsöversikt (refereegranskat)abstract
- Direct measurements of the force between hydrophobic surfaces across aqueous solutions are reviewed. The results are presented according to the method of preparation of the hydrophobic surfaces. No single model appears to fit all published results, and an attempt is made to classify the measured interactions in three different categories. The large variation of the measured interaction, often within each class, depending on the type of hydrophobic surface is emphasized. (I) Stable hydrophobic surfaces show only a comparatively short-range interaction, although little quantitative data on this attraction have been published. (II) Many results showing very long-range attractive forces are most likely due to the presence of sub-microscopic bubbles on the hydrophobic surfaces. Such an interaction is typically measured between silica surfaces made hydrophobic by silylation. Between self-assembled thiol layers on gold surfaces very short-range attractive forces are possibly due to the presence or nucleation of bubbles. The reason for the apparent stability of these bubbles is not clear and warrants further investigation. (III) Results obtained with LB films of surfactants or lipids on mica appear to give rise to a different type of force that fits neither of these two categories. This force is an exponentially decaying attraction, often of considerable range. The force turns more attractive at smaller separations, and may at short range be similar to the interaction measured between stable hydrophobic surfaces. An apparently similar, exponential attraction is also found between mica surfaces bearing surfactants adsorbed from cyclohexane, between silylated, plasma-treated mica surfaces and between both mica and silica surfaces with surfactants adsorbed in situ. This type of force also occurs between some surfaces of relatively low hydrophobicity as well as between one such hydrophobic surface and a hydrophilic surface. No convincing model can explain this third type of interaction for all systems in which it has been observed. This review of work to date points to the importance of the morphology and structure of the hydrophobic surface, and how it may change during the interaction of two surfaces.
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| 5. |
- 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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| 6. |
- Claesson, Hans, et al.
(författare)
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Semi-crystalline thermoset resins : tailoring rheological properties in melt using comb structures with crystalline grafts
- 2004
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Ingår i: Progress in organic coatings. - : Elsevier BV. - 0300-9440 .- 1873-331X. ; 49:1, s. 13-22
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Tidskriftsartikel (refereegranskat)abstract
- Thermosetting resins with semi-crystalline grafts have been synthesized. An amorphous resin with epoxide groups was first functionalized with hydroxyl groups using 2,2-bis(methylol) propionic acid, bis-MPA in bulk at 155 degreesC. Functionalization with bis-MPA was monitored using FT-IR, FT-Raman and SEC. The reaction was complete in 30 min. Grafts of poly(epsilon-caprolactone) were then grown from the hydroxyl functional resin and end capped with methacrylate groups. The polymerization Of epsilon-caprolactone, performed in bulk at 110 degreesC using Sn(Oct)(2), was characterized using H-1 NMR and SEC. The obtained molecular weights agreed well with theoretical values. The final end capping was performed using methacrylic anhydride, and monitored with SEC and H-1 NMR, which indicated full substitution. Two combs were synthesized with different arm lengths, DP 10 and 20, and the obtained M-W were close to calculated values. The complex viscosity was measured from low to high temperature for the crystalline resins, the amorphous resin and blends thereof. Rheological data show a rapid decrease in viscosity within a temperature change of 10-15 degreesC for the crystalline resins while the amorphous resin exhibited a slow softening. The blends exhibited a behavior in-between that of the crystalline and the amorphous resin. Films were prepared from the pure resins and the blends. The films were cured using UV irradiation. The comb architecture of these resins has advantages such as crystallinity, high molecular weight and low viscosity, facilitating leveling and resulting in smooth films. The final film properties varied with the ratio of crystalline to amorphous resin, where increase in the amount of crystalline resin correlated with increased the flexibility.
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| 7. |
- Claesson, Hans, et al.
(författare)
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Synthesis and characterisation of star branched polyesters with dendritic cores and the effect of structural variations on zero shear rate viscosity
- 2002
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 43:12, s. 3511-3518
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Tidskriftsartikel (refereegranskat)abstract
- A series of branched polyesters consisting of poly(epsilon-caprolactone) (PCL) (degree of polymerisation: 5-200) initiated from hydroxy-functional cores and end-capped with methylmethacrylate have been prepared. The cores were third-generation hyperbranched polyester, Boltorn, with approximately 32 hydroxyl groups, a third-generation dendrimer with 24 hydroxyl groups and a third-generation dendron with eight hydroxyl groups. Finally, a linear PCL was synthesised as a reference material. All initiators were based on 2,2-bis(methylol) propionic acid (bis-MPA). C-13 NMR spectra of the polymers showed that those with shorter arms contained unreacted hydroxyl groups on the core. Rheological measurements of zero shear rate viscosity, eta(0), showed that the branched polyesters had a considerably lower eta(0) than linear polyester with similar molecular weight. The low melt viscosity and the crystallity produced a theological behaviour suitable for the film formation process for powder coatings. Measurements of mechanical properties of cured films showed that those with low arm molecular weight, M-a, were amorphous while those of high M-a were crystalline.
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| 10. |
- Ederth, Thomas, et al.
(författare)
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Force measurements between semifluorinated thiolate self-assembled monolayers : Long-range hydrophobic interactions and surface charge
- 2001
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 235:2, s. 391-397
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Tidskriftsartikel (refereegranskat)abstract
- Long-range interactions between self-assembled monolayers (SAMs) of semifluorinated alkanethiols have been studied by direct force measurements in water and aqueous NaCl solutions. SAMs prepared from three different thiols, with identical fluorinated head groups but varying hydrocarbon spacer lengths, were investigated: CF3(CF2)(9)(CH2)(x)SH, where x = 2, 11, or 17. Force measurements show that the interactions in water and electrolyte solutions are composed of both double-layer interactions emerging from what appears to be charges adsorbed onto the surfaces and long-range "hydrophobic" attractions, in excess of the expected van der Waals forces. The three investigated thiols produce similar results in force measurements, though the contact angles with water are slightly different, The "hydrophobic" attraction has the form of step-like attractive discontinuities in the force profiles at separations ranging from 20 to 40 nm, caused by bridging of microscopic bubbles residing at the surfaces, The shape or range of these discontinuities are not significantly affected by replacement of the water with either 1 mM or 1 M NaCl solutions. The origin of the charges causing the electrostatic double-layer interaction is unclear, but some possible causes are discussed.
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| 13. |
- 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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| 16. |
- 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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| 18. |
- Mattson, Maria K., et al.
(författare)
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Adsorption of Alkyl Polyglucosides on the Solid/Water Interface : Equilibrium Effects of Alkyl Chain Length and Head Group Polymerization
- 2004
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:10, s. 4051-4058
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Tidskriftsartikel (refereegranskat)abstract
- The equilibrium adsorption behavior of two n-alkyl-beta-D-glucosides (octyl (C(8)G(1)) and decyl (C(10)G(1))) and four n-alkyl-beta-D-maltosides (octyl(C(8)G(2)), decyl (C,(10)G(2)), dodecyl(C(12)G(2)) and tetradecyl (C(14)G(2))) from aqueous solution on a titania surface, as measured by ellipsometry, has been investigated. The main focus has been on the effect of changes in the alkyl chain length and headgroup polymerization, but a comparison with their adsorption on the silica/water and air/water interfaces is also presented. Some comparison with the corresponding adsorption of ethylene oxide surfactants, in particular C10E6 and C12E6, is given as well. For all alkyl polyglucosides, the maximum adsorbed amount on titania is reached slightly below the critical micelle concentration (cmc), where it levels off to a plateau and the amount adsorbed corresponds roughly to a bilayer. However, there is no evidence that this is the actual conformation of the surfactant assemblies on the surface, but the surfactants could also be arranged in a micellar network. On hydrophilic silica, the adsorbed amount is a magnitude lower than on titania, corresponding roughly to a layer of surfactants lying flat on the surface. A change in the alkyl chain length does not result in any change in the plateau molar adsorbed amount at equilibrium; however, the isotherm slope for the alkyl maltosides increases with increasing chain length. Headgroup polymerization on the other hand affects the adsorbed amount. The alkyl glucosides start adsorbing at lower bulk concentrations than the maltosides and equilibrate at higher adsorbed amounts above the cmc. When compared with the ethylene oxide (EO) surfactants, it is confirmed that the EO surfactants hardly adsorb on titania, since the measured changes in the ellipsometric angles are within the noise level. They do, however, adsorb strongly on silica.
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| 21. |
- Persson, C. M., et al.
(författare)
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Interfacial behavior of n-decyl-beta-D-maltopyranoside on hydrophobic interfaces and the effect of small amounts of surface-active impurities
- 2002
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 251:1, s. 182-192
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Tidskriftsartikel (refereegranskat)abstract
- The effect of small amounts of surface-active impurities on the interfacial properties of n-decyl-beta-D-maltopyranoside was investigated using various methods. The n-Decyl-beta-D-maltopyranoside was used both as received from Sigma (<98% by GC) and after being purified with the surfactant-purifying apparatus developed by Lunkenheimer, which removes impurities that are more surface active than the major component. Surface tension measurements demonstrate that the surface elasticity of the surfactant-loaded liquid-vapor interface increased after purification. Measurements of interactions across single foam films revealed that the purified solution formed considerably less charged and less stable films compared with the as-received sample. These results are consistent with the lower foam stability for the purified sample as determined by simple shaking experiments. The lower film stability for the purified solution was attributed to the lower double-layer force. The forces acting between spherical silanated glass surfaces across surfactant solutions were determined with the MASIF (measurement and analysis of surface interaction forces) technique. On approach, the same interactions were experienced in solutions of the as-received and purified surfactant. On the other hand, the adhesion force was lower after purification. Both for the as-received and the purified sample it was observed that the adhesion increased with increasing contact time up to a certain limit. This was explained in terms of partial pressure-induced desorption of surfactants from the disordered silane layers. Wetting experiments also indicated that the surfactants were difficult to remove completely from this surface.
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| 22. |
- Rippner Blomqvist, Brita, et al.
(författare)
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Interfacial films of poly(ethylene oxide)-poly(butylene oxide) block copolymers characterized by disjoining pressure measurements, in situ ellipsometry, and surface tension measurements
- 2002
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 18:13, s. 5213-5221
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Tidskriftsartikel (refereegranskat)abstract
- Interactions between two air-water interfaces stabilized by poly(ethylene oxide)-poly(butylene oxide) block copolymers were investigated by employing the microinterferometric thin-film balance technique. A series of three block copolymers, two linear diblock copolymers, B8E41 and E106B16, and one linear triblock copolymer, E21B8E21, were investigated. In particular the range of the steric forces operating across the thin foam films was quantified. As expected, higher concentrations, were required of the triblock copolymer than for the diblocks for the formation of a stable foam film. Despite the low polydispersity of the sample (M-w/M-n = 1.03), effects due to polydispersity on the concentration dependence of the disjoining pressure isotherm were noted. Furthermore, the adsorption at the air-water interface was determined by surface tension measurements. It was noted that long equilibrium times are required to obtain (quasi) equilibrium surface tension data. Time-resolved ellipsometry was used to follow the adsorption rates and determine the amounts adsorbed in situ at hydrophobic solid surfaces. The adsorbed amount at the solid-liquid interface determined by ellipsometry was similar to that at the air-water interface estimated from the surface tension isotherm provided polydispersity effects on the surface tension isotherm were taken into account. Moreover, interactions in foam films formed from mixtures of the diblock copolymer, B8E41, and a cationic surfactant, hexadecyltrimethylammonium bromide, were studied. Both electrostatic double-layer forces and, at shorter range, steric forces were present, demonstrating the formation of a mixed layer at the interface.
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| 23. |
- Rojas, Orland J., et al.
(författare)
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Coadsorption and surface forces for selective surfaces in contact with aqueous mixtures of oppositely charged surfactants and low charge density polyelectrolytes
- 2004
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:8, s. 3221-3230
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Tidskriftsartikel (refereegranskat)abstract
- The coadsorption of a positively charged polyelectrolyte (with 10% of the segments carrying a permanent positive charge, AM-MAPTAC-10) and an anionic surfactant (sodium dodecyl sulfate, SDS) on silica and glass surfaces has been investigated using optical reflectometry and a noninterferometric surface force technique. This is a selective coadsorption system in the sense that the polyelectrolyte does adsorb to the surface in the absence of surfactant, whereas the surfactant does not adsorb in the absence of polyelectrolyte. It is found that the total adsorbed amount goes through a maximum when the SDS concentration is increased. Maximum adsorption is found when the polyelectrolyte/surfactant complexes formed in bulk solution are close to the charge neutralization point. Some adsorption does occur also when SDS is present in significant excess. The force measured between AM-MAPTAC-10-coated surfaces on approach in the absence of SDS is dominated at long range by an electrostatic double-layer force. Yet, layers formed by coadsorption from solutions containing both polyelectrolyte and surfactant generate long-range forces of an electrosteric nature. On separation, adhesive interactions are found only when the adsorbed amount is low, i.e., in the absence of SDS and in a large excess of SDS. The final state of the adsorbed layer is found to be nonhysteretic, i.e., independent of the history of the system. The conditions for formation of long-lived trapped adsorption states from mixed polymer-surfactant solutions are discussed.
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| 27. |
- 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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| 28. |
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| 29. |
- Wu, Jufang, et al.
(författare)
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Measurement and Prediction of the Adsorption of Binary Mixtures of Organic Vapours on Activated Carbon
- 2001
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Ingår i: Adsorption Science and Technology. ; 19:9, s. 737-49
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a modified headspace method for measuring the adsorption equilibrium of mixtures of organic vapours. The advantage of the method relative to the ordinary headspace method is the shorter time needed to reach adsorption equilibrium. The adsorption isotherms of benzene, hexane and pentane on activated carbons were acquired quickly and easily using this method. The method has also been used to measure the binary equilibrium data of benzene- hexane, benzene-pentane and hexane-pentane mixtures on three types of activated carbon. The 'Ideal Adsorbed Solution Theory' (IAST) was used to predict the binary adsorption equilibria from the adsorption isotherms for the single components. Good agreement was obtained between prediction and measurement for the total amount of components adsorbed, as well as for the ratio of compounds in the adsorbed phase. The small deviation noted was probably a result of using the Freundlich adsorption isotherm in IAST modelling.
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