| 1. |
- Petersson, Göran, 1941
(författare)
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Conversion of dehydroascorbic acid to a branched hexaric acid in neutral and alkaline aqueous solution
- 1976
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Ingår i: Analytical Biochemistry. - : Elsevier BV. - 0003-2697. ; 72, s. 623-628
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Tidskriftsartikel (refereegranskat)abstract
- Dehydroascorbic acid is shown to be converted to 2-(threo-1,2,3-trihydroxypropyl)tartronic acid in aqueous alkaline solutions. The structure of the acid was determined by mass spectrometry of its acyclic Me3Si derivative. Mass spectrometric and chromatographic data are compared with those of related compounds. The acid is formed by a benzilic acid rearrangement of the intermediate 2,3-hexodiulosonic acid. The rate of formation at 38°C was studied quantitatively by glc. It increases at increased alkalinity but is significant even at physiological pH. The presence of oxygen does not substantially influence the reaction.
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| 2. |
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| 3. |
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| 4. |
- Ask, Per, 1950-, et al.
(författare)
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Clinical evaluation of different fluid-filled systems for oesophageal manometry
- 1979
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Ingår i: Scandinavian Journal of Gastroenterology. - 0036-5521 .- 1502-7708. ; 14:1, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- In a clinical study of oesophageal manometry with fluid-filled catheters, both a non-perfused system and a perfused system with a syringe pump have been compared to a system with a low-compliance perfusion pump, which served as a reference. Significantly lower values of motility amplitudes, motility derivatives, and partly of LES pressures, and a time delay of up to 0.5 sec of the amplitude maximum were obtained with the non-perfused system and the system with a syringe pump in comparison to the low-compliance system. Since the oesophageal function can be erroneously evaluated by use of a non-perfused system or a perfused system with a syringe pump, such systems cannot be recommended for clinical use.
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| 5. |
- Ask, Per, 1950-, et al.
(författare)
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ECG Electrodes : A Study of Electrical and Mechanical Long-term Properties
- 1979
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Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 23:2, s. 189-206
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Tidskriftsartikel (refereegranskat)abstract
- The long-term properties of commercially available ECG-electrodes were studied by investigating the parameters: polarization potential, electrical impedance, adhesion, and skin reactions during a period of 7 days. As expected, the most stable polarization potentials were obtained for Ag/AgCl electrodes. Certain simple disposable electrodes showed large polarization potential variations. The most stable electrode impedance was obtained for disposable electrodes with stable adhesion and equipped with an electrode cup or similar. Unchanged adhesion and mechanical properties during the test period were shown by the disposable electrodes with a large self-adhesive collar.
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| 6. |
- Ask, Per, et al.
(författare)
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Mechanisms affecting lower oesophageal sphincter opening and oesophageal retention : A combined X-ray and manometry study
- 1978
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Ingår i: Scandinavian Journal of Gastroenterology. - 0036-5521 .- 1502-7708. ; 13:7, s. 857-861
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Tidskriftsartikel (refereegranskat)abstract
- Using simultaneous manometry and cineradiography, oesophageal evacuation was studied while contrast medium was infused via a catheter. The distal half of the oesophagus could be filled with contrast medium without triggering peristalsis. The hydrostatic pressure necessary to open the lower oesophageal sphincter (LES) was of approximately the same magnitude as the pressure gradient between oesophagus and LES. No significant relaxation of the LES could be observed at the initiation of swallowing. The LES may be looked upon not only as a sphincter preventing reflux but also as a gate which must be forced open by food.
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| 7. |
- Ask, Per, et al.
(författare)
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Static and dynamic characteristics of fluid-filled esophageal manometry systems
- 1977
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Ingår i: American Journal of Physiology. - 0002-9513. ; 233:5, s. E389-E396
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Tidskriftsartikel (refereegranskat)abstract
- Esophageal manometric systems with water-filled catheters have been characterized by the use of model experiments. The examined parameters have been: catheter dimension, catheter compliance, catheter resistance, pump type, pump compliance, and perfusion flow. Accurate static pressure measurements have been obtained for perfused systems independently of the investigated parameters. The dynamic characteristics vary with catheter diameter and perfusion flow. For catheters with low diameter, a narrow bandwidth is obtained for the investigated perfusion flows. The results have been expressed in terms of an electric model of the measurement system. Perfusion pumps with low compliance are recommended to improve the dynamic properties of the measurement system.
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