| 1. |
- Barclay, Susan A, et al.
(författare)
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The shape of the proximal isovelocity surface area varies with regurgitant orifice size and distance from orifice : computer simulation and model experiments with color M-mode technique.
- 1993
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Ingår i: Journal of the American Society of Echocardiography. - 0894-7317 .- 1097-6795. ; 6:4, s. 433-445
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Tidskriftsartikel (refereegranskat)abstract
- The hemispheric proximal isovelocity surface area method for quantification of mitral regurgitant flow (i.e., Qc = 2 pi r2v), where 2 pi r2 is the surface area and v is the velocity at radius r, was investigated as distance from the orifice was increased. Computer simulations and steady flow model experiments were performed for orifices of 4, 6, and 8 mm. Flow rates derived from the centerline velocity and hemispheric assumption were compared with true flow rates. Proximal isovelocity surface area shape varied as distance from each orifice was increased and could only be approximated from the hemispheric equation when a certain distance was exceeded: > 7, > 10, and > 12 mm for the 4, 6, and 8 mm orifices, respectively. Prediction of relative error showed that the best radial zone at which to make measurements was 5 to 9, 6 to 14 and 7 to 17 mm for the 4, 6, and 8 mm orifices, respectively. Although effects of a nonhemispheric shape could be compensated for by use of a correction factor, a radius of 8 to 9 mm can be recommended without the use of a correction factor over all orifices studied if a deviation in calculated as compared with true flow of 15% is considered acceptable. These measurements therefore have implications for the technique in clinical practice.
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| 2. |
- Edlund, Per-Olov, et al.
(författare)
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Forecasting the Swedish unemployment rate. VAR vs. transfer function modelling
- 1993
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Ingår i: International Journal of Forecasting. - : Elsevier. - 0169-2070 .- 1872-8200. ; 9:1, s. 61-76
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Tidskriftsartikel (refereegranskat)abstract
- The Swedish unemployment rate is forecast using three time series methods: the ARIMA, transfer function and Vector Autoregressive (VAR) models. Within this context, the choice of modelling strategy is discussed. It is found that the forecasting performance of VAR models is improved by explicitly taking account of cointegration between the variables in the model, despite the fact that unemployment is not cointegrated. However, the more parsimonious ARIMA and transfer function models have lower RMSE for all forecasting horizons. It is also found that the additional variables in the VAR models are important for predicting the turning points in the unemployment rate.
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| 3. |
- Karlsson, Magnus K., et al.
(författare)
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Bone mineral normative data in Malmö, Sweden : Comparison with reference data and hip fracture incidence in other ethnic groups
- 1993
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Ingår i: Acta Orthopaedica. - : Medical Journals Sweden AB. - 1745-3674 .- 0001-6470. ; 64:2, s. 168-172
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Tidskriftsartikel (refereegranskat)abstract
- The bone mineral mass was measured in 324 residents of the city of Malmö Sweden, by dual energy roentgen absorptiometry (DEXA) using the Lunar DPX equipment - total body, hip, and lumbar vertebrae. the bone mineral content of the wrist was also measured with single photon absorptiometry (SPA) in 88 of the individuals. Weight, height, and vertebral height, as well as body fat, lean body mass, menarcheal age, menopausal age, and hand grip strength were determined. Measurements were compared with reference bone mineral content values from the United States, Japan, and France - also hip fracture incidence was compared. All bone mineral values decreased with age. A good correlation was found between the DEXA technique of total body bone mineral and the forearm SPA values. the bone mineral content was correlated with lean body mass and weight. the Malmö bone mineral content was on the same level as in the United States, but higher than in Japan and France. the comparatively high risk of fragility fractures in the Scandinavian countries compared with most other settings cannot be explained by low bone mass.
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| 4. |
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