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- Johansson, Rolf
(författare)
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Parametric Models of Linear Multivariable Systems for Adaptive Controllers
- 1982
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Ingår i: Proc. 21st IEEE Conference on Decision and Control (CDC'82), Orlando, FL, December 1982. ; , s. 989-989
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Konferensbidrag (refereegranskat)abstract
- This paper presents a parametrization scheme for adaptive control of linear, multivariable systems with strictly proper transfer functions. The required a priori information consists of the internal structure matrix BS * and appropriate polynomial degrees.
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- Johansson, Rolf, 1952-
(författare)
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Stereo and regio controlled halogenation, and synthesis of low molecular weight carbohydrates
- 1984
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The regio- and stereoselective introduction of halogens as well as unsaturation into carbohydrates is investigated with triphenylphosphine - halide systems. Three different glycosidation methods are presented. For the synthesis of 1,2-cis mannopyranosides a mannosyl chloride with nonparticipating cyclohexylidene groups is used, and for the synthesis of 1,2-trans gluco- and galactopyranosides acetylated glycosyl halides and new activating systems are examined.
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- Holm, M, et al.
(författare)
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Effect of cardiac exposure by median sternotomy on atrial fibrillation cycle length
- 1999
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Ingår i: Europace. - : Oxford University Press (OUP). - 1532-2092 .- 1099-5129. ; 1:4, s. 248-257
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Epicardial mapping is a powerful tool that has enabled us to gain insight into the electrical phenomena perpetuating atrial fibrillation and has guided the design of surgical and catheter-based therapeutic strategies. However, epicardial data are acquired during abnormal physiological conditions; the patients are anaesthetized, their chests opened, dislocating the heart and exposing it to air of room temperature, and the autonomic tone is modulated due to the surgery. The effect of intra-operative conditions on atrial electrophysiological properties have not been investigated before. Thus in the present study we assessed the atrial cycle length, shown to be an index of atrial refractoriness, and the ventricular rate before and during open-heart surgery in 10 patients with chronic atrial fibrillation and an underlying heart disease. METHODS AND RESULTS: Using a newly introduced and validated ECG method known as frequency analysis of fibrillatory ECG (FAF-ECG), the atrial cycle length and the ventricular rate were determined just before surgery. After anaesthesia and median sternotomy, epicardial mapping of the entire right atrial free wall was performed. The mean ventricular rate as well as the dominant atrial fibrillation cycle length consistently increased, the former from 71 to 92 beats x min(-1) (mean of all patients, P<0.05) and the latter from 156 to 172 ms (P<0.05). CONCLUSIONS: Atrial fibrillation cycle length, an index of atrial refractoriness, is increased as an effect of anaesthesia and heart exposure during open-heart surgery in patients with chronic atrial fibrillation, implying that atrial activation might be altered, which must be considered when interpreting data from epicardial conduction analysis.
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- Holm, Magnus, et al.
(författare)
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Epicardial right atrial free wall mapping in chronic atrial fibrillation. Documentation of repetitive activation with a focal spread--a hitherto unrecognised phenomenon in man
- 1997
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Ingår i: European Heart Journal. - : Oxford University Press (OUP). - 1522-9645 .- 0195-668X. ; 18:2, s. 290-310
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Previous studies have shown that atrial fibrillation of recent onset in man is based on a varying number of simultaneously present activation waves reentering either themselves or each other. In the present study, right atrial activation during chronic atrial fibrillation in man was studied. METHODS AND RESULTS: In 16 patients with chronic atrial fibrillation multiple epicardial recordings of 8 s each were made at the right atrial posterior free wall and at the appendage using a 20 x 35 mm electrode array with 56 bipolar measurement points. The preferable activation pattern of each recording and the propagation direction, cycle length and conduction velocity of individual activation waves within each recording were determined. Activation was characterized by unorganised activation with several simultaneously present activation waves: inconsistent preferable activation pattern (n = 5), predominantly organised activation with either frequent episodes of uniform activation: consistent preferable activation pattern (n = 7) or frequent episodes of activation with focal spread; focal preferable activation pattern (n = 4). Random re-entry was frequently documented in recordings with the inconsistent preferable activation pattern and less frequently in recordings with the consistent and focal preferable activation pattern. Complete re-entry circuits were rarely documented. The median fibrillation cycle length was 146, 159 (P < 0.05) and 165 ms (not significant) and the mean conduction velocity during uniform activation was 64, 67 and 83 cm. s-1 (not significant) in recordings with the inconsistent, consistent and focal preferable activation pattern, respectively. CONCLUSIONS: During chronic atrial fibrillation in man, right atrial free wall activation ranges from disorganised activation with multiple co-existing activation waves to predominantly organised activation characterized by either uniform activation consistent with the presence of large re-entry circuits or repetitive activation of unknown mechanism and focal spread.
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