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- Piispanen, PS, et al.
(författare)
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Synthesis and surface measurements of surfactants derived from dehydroabietic acid
- 2003
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Ingår i: Journal of Surfactants and Detergents (JSD). - 1097-3958 .- 1558-9293. ; 6, s. 125-130
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Tidskriftsartikel (refereegranskat)abstract
- Dehydroabietates with poly(ethylene oxide) chains of average m=12, 17 and 45 units (DeHab(E)m) have been synthesized and some of their surfactant properties have been characterized. The results have been compared with common linear chain CnEm surfactants. The adsorption to the liquid-vapor interface was measured and the adsorbed amount and critical micelle concentrations, cmc, determined. The dehydroabietic acid as hydrophobe was found to result in the same cmc as a linear dodecyl chain. The DeHAb(E)45 was found to be insoluble above 400 mg/l, but the surface tension at lower concentrations were similar to those of the C11-13E38-40 surfactants, which exhibit cmcs in aqueous media. The reason for the insolubility of DeHab(E)45 is proposed to be the large size and rigid structure of the hydrophobe, which imposes a large micelle size. The curvature of such a micelle is too low for efficient packing of the large headgroup, so micelle formation becomes unfavorable. The foaming behavior of the DeHAb(E)12 and DeHab(E)17 surfactants was about the same as for common linear CnEm surfactants i.e. the foamability as well as the foam stability increased with ethylene oxide chain length. The cloud point was depressed by increased salt concentration and increased with the number of ethylene oxide units in the head-group. The cloud point was significantly lower than for the corresponding surfactant with a dodecyl chain with similar EO-chain length. The suggested reason for this is explained by the fact that the micelles of DeHab(E)m are larger, due to the large and more rigid dehydroabietic hydrophobe. The attractive forces between the micelles are larger for DeHab(E)m than for the linear CnEm surfactants. The more concentrated surfactant phase of DeHab(E)m leads to clouding phenomenon at lower temperatures than for CnEm. The wetting results, obtained by measuring the contact angle at similar surface tensions, indicate that surfactants of the DeHab(E)m type are more efficient wetting agents than both disaccharide sugar surfactants and CnEm type surfactants.
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- Strom, P., et al.
(författare)
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Validation and learning in the Procedicus KSA virtual reality surgical simulator : Implementing a new safety culture in medical school
- 2003
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Ingår i: Surgical Endoscopy. - : Springer Science and Business Media LLC. - 0930-2794 .- 1432-2218. ; 17:2, s. 227-231
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Tidskriftsartikel (refereegranskat)abstract
- Background: Advanced simulator training within medicine is a rapidly growing field. Virtual reality simulators are being introduced as cost-saving educational tools, which also lead to increased patient safety. Methods: Fifteen medical students were included in the study. For 10 medical students performance was monitored, before and after 1 h of training, in two endoscopic simulators (the Procedicus KSA with haptic feedback and anatomical graphics and the established MIST simulator without this haptic feedback and graphics). Five medical students performed 50 tests in the Procedicus KSA in order to analyze learning curves. One of these five medical students performed multiple training sessions during 2 weeks and performed more than 300 tests. Results: There was a significant improvement after 1 h of training regarding time, movement economy, and total score. The results in the two simulators were highly correlated. Conclusion: Our results show that the use of surgical simulators as a pedagogical tool in medical student training is encouraging. It shows rapid learning curves and our suggestion is to introduce endoscopic simulator training in undergraduate medical education during the course in surgery when motivation is high and before the development of "negative stereotypes" and incorrect practices.
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- Öhlin, Bertil, et al.
(författare)
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Dual versus triple therapy in eradication of Helicobacter pylori
- 2002
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Ingår i: Hepato-Gastroenterology. - 0172-6390. ; 49:43, s. 172-175
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Tidskriftsartikel (refereegranskat)abstract
- Background/Aims: Duodenal ulcers should be treated by eradication of Helicobacter pylori. This study compared the efficacy of a proton pump inhibitor together with one or two antibiotics in eradication therapy, Methodology: 177 patients who were H. pylori positive were randomized to receive 14 days of either: lansoprazole 30mg bd and amoxicillin 1g bd (LA), omeprazole 20mg bd and amoxicillin 1g bd (OA) or lansoprazole 30mg bd, amoxicillin 1g bd and clarithromycin 500mg bd (LAC). The efficacy was assessed at four weeks and at six months after the end of treatment. Biopsies were taken for culture and bacterial sensitivity testing at inclusion and at four weeks after the end of treatment. Results: 149 patients were evaluated for efficacy. The eradication rate was significantly higher in LAC (96%) compared to LA (51%) and OA (64%) treatments (P<0.001). At baseline 17%, 21% and 19% of the patients in the LA, OA and LAC groups, respectively, were resistant to metronidazole and only one patient was resistant to clarithromycin. Post-treatment, four patients had acquired metronidazole resistance. Conclusions: LAC is more effective than LA and CA for eradication of H. pylori in duodenal ulcer disease.
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