Does the Box-Cox transformation help in forecasting macroeconomic time series?

The paper investigates whether transforming a time series leads to an improvement in forecasting accuracy. The class of transformations that is considered is the Box-Cox power transformation, which applies to series measured on a ratio scale. We propose a nonparametric approach for estimating the optimal transformation parameter based on the frequency domain estimation of the prediction error variance, and also conduct an extensive recursive forecast experiment on a large set of seasonal monthly macroeconomic time series related to industrial production and retail turnover. In about one fifth of the series considered the Box-Cox transformation produces forecasts significantly better than the untransformed data at one-step-ahead horizon; in most of the cases the logarithmic transformation is the relevant one. As the forecast horizon increases, the evidence in favour of a transformation becomes less strong. Typically, the naïve predictor that just reverses the transformation leads to a lower mean square error than the optimal predictor at short forecast leads. We also discuss whether the preliminary in-sample frequency domain assessment conducted provides a reliable guidance which series should be transformed for improving significantly the predictive performance

Chronische centrale cyanose bij kinderen; altijd een reden voor nadere diagnostiek

Contains fulltext : 25438___.PDF (publisher's version ) (Open Access

Essential improvements to a working, isolated rat heart model with hemodynamic and NMR spectroscopic monitoring

Contains fulltext : 25795___.PDF (publisher's version ) (Open Access

Concomitant coronary artery revascularization and right pneumonectomy without cardiopulmonary bypass

Combined coronary artery bypass grafting (CABG) and pneumonectomy has a high morbidity and mortality rate, especially when the right lung has to be removed. A patient is described who underwent a CABG operation through a midline sternotomy without the use of cardiopulmonary bypass (CPB), and a right pneumonectomy through a right lateral thoracotomy in one operative session. To our knowledge, this is the first case in which this operative strategy was employed. CABG operations without the use of CPB might put concomitant lung surgery in a new perspective

Frequency and outcome of re-interventions after endovascular repair for abdominal aortic aneurysm: A prospective cohort study:A prospective cohort study

AbstractPurpose. To describe frequency, type, and outcome of re-intervention after endovascular aortic aneurysm repair (EVAR).Methods. Between September 1996 and December 2003, 308 patients were treated, with data collected prospectively. No patient was lost to follow up, but two were excluded (one primary conversion, and one post-operative death). Vanguard, Talent, Excluder, Zenith, and Quantum devices were used. Follow up required a CT scan before discharge. Initially, a CT scan was done at each follow up. Subsequently, we used duplex ultrasound and abdominal X-ray, with CT scan used selectively.Results. Mean follow-up was 36±22 months. Re-interventions were required in 47 (15%) patients, 31 (66%) elective and 16 (34%) emergency cases. In 32 patients, the primary re-intervention was successful; in 15 patients an additional 13 secondary and four tertiary re-interventions were required. A total of 72 adjunctive manoeuvres were performed: 49 endovascular (68%) and 23 open (32%). The success of endovascular re-interventions was 80%. The success of open re-interventions was 96%. Open conversions were required in nine patients (3%). There was no mortality.Conclusion. EVAR was associated with a low burden of re-interventions, with only 15% patients requiring re-intervention. Our long-term follow up, without regular CT, was simple and effective