Jörg A. Walter

The greenhouse effect: Damages, costs and abatement

The buildup of so-called “greenhouse gases” in the atmosphere — CO2 in particular-appears to be having an adverse impact on the global climate. This paper briefly reviews current expectations with regard to physical and biological effects, their potential costs to society, and likely costs of abatement. For a “worst case” scenario it is impossible to assess, in economic terms, the full range of possible non-linear synergistic effects. In the “most favorable” (although not necessarily “likely”) case (of slow-paced climate change), however, it seems likely that the impacts are within the “affordable” range, at least in the industrialized countries of the world. In the “third world” the notion of affordability is of doubtful relevance, making the problem of quantitative evaluation almost impossible. We tentatively assess the lower limit of quantifiable climate-induced damages at

A tactile sensor system for a three-fingered robot manipulator

30 to

Rapid learning with parametrized self-organizing maps

35 per ton of “CO2 equivalent”, worldwide, with the major damages being concentrated in regions most adversely affected by sea-level rise. The non-quantifiable environmental damages are also significant and should by no means be disregarded.The costs and benefits of (1) reducing CFC use and (2) reducing fossil fuel consumption, as a means of abatement, are considered in some detail. This strategy has remarkably high indirect benefits in terms of reduced air pollution damage and even direct cost savings to consumers. The indirect benefits of reduced air pollution and its associated health and environmental effects from fossil-fuel combustion in the industrialized countries range from

Nonlinear prediction with self-organizing maps

20 to

Creatinine clearance versus serum creatinine as a risk factor in cardiac surgery

60 per ton of CO2 eliminated. In addition, there is good evidence that modest (e.g. 25%) reductions in CO2 emissions may be achievable by the U.S. (and, by implication, for other countries) by a combination of increased energy efficiency and restructuring that would permit simultaneous direct economic benefits (savings) to energy consumers of the order of

Preoperative high leukocyte count: a novel risk factor for stroke after cardiac surgery

50 per ton of CO2 saved. A higher level of overall emissions reduction — possibly approaching 50% — could probably be achieved, at little or not net cost, by taking advantage of these savings.We suggest the use of taxes on fossil fuel extraction (or a carbon tax) as a reasonable way of inducing the structural changes that would be required to achieve significant reduction in energy use and CO2 emissions. To minimize the economic burden (and create a political constituency in support of the approach) we suggest the substitution of resource-based taxes in general for other types of taxes (on labor, income, real estate, or trade) that are now the main sources of government revenue. While it is conceded that it would be difficult to calculate the “optimal” tax on extractive resources, we do not think this is a necessary prerequisite to policy-making. In fact, we note that the existing tax system has never been optimized according to theoretical principles, and is far from optimal by any reasonable criteria.

Is age an independent determinant of mortality in cardiac surgery as suggested by the EuroSCORE

Tactile sensor systems are an essential prerequisite for the implementation of complex manipulation and exploration tasks using robots. The desire to perform real-time control and pattern recognition with tactile sensors led us to the design of a cost-effective artificial fingertip. At our laboratory two distinct types of sensors are in use: force/position sensors and slippage detectors. We report on first experimental results with a fingertip prototype performing rolling and sliding movements over a flat surface. To facilitate experimentation with tactile sensors, we designed and developed a data acquisition and transportation system that fulfils our demands on bandwidth, flexibility, and cost. This system consists of two hardware components, a configurable multichannel analog signal sampler to acquire sensor data, and an intelligent dual-ported random-access buffer to avoid data transportation bottlenecks.

Impact of age on the results of coronary artery bypass grafting.

Abstract The construction of computer vision and robot control algorithms from training data is a challenging application for artificial neural networks. However, many practical applications require an approach that is workable with a small number of data examples. In this contribution, we describe results on the use of ‘Parametrized Self-organizing Maps’ (‘PSOMs’) with this goal in mind. We report results that demonstrate that a small number of labeled training images is sufficient to construct PSOMs to identify the position of finger tips in images of 3D-hand shapes to within an accuracy of only a few pixel locations and we present a framework of hierarchical PSOMs that allows rapid ‘ one-shot-learning ’ after acquiring a number of ‘basis mappings’ during a previous ‘investment learning stage’ . We demonstrate the potential of this approach with the task of constructing the position-dependent mapping from camera coordinates to the work space coordinates of a Puma robot.

Is there any impact of the shape of aortic end-hole cannula on stroke occurrence? Clinical evaluation of straight and bent-tip aortic cannulae

The problem of predicting highly nonlinear time sequence data, where the usual approach using adaptive linear regressive models encounters difficulty, is considered. For this case, the use of an adaptive covering of the state space of the process with a set of linear regressive models, each of which is only locally used, is suggested. It is shown that such an adaptive covering, together with learning of the appropriate prediction coefficients, can be realized using Kohonens algorithm of self-organizing maps. To illustrate the method, simulation results for a set of benchmarking problems are given

Interactive visualization and navigation in large data collections using the hyperbolic space

BackgroundRenal impairment is one of the predictors of mortality in cardiac surgery. Usually a binarized value of serum creatinine is used to assess the renal function in risk models. Creatinine clearance can be easily estimated by the Cockcroft and Gault equation from serum creatinine, gender, age and body weight. In this work we examine whether this estimation of the glomerular filtration rate can advantageously replace the serum creatinine in the EuroSCORE preoperative risk assessment.MethodsIn a group of 8138 patients out of a total of 11878 patients, who underwent cardiac surgery in our hospital between January 1996 and July 2002, the 18 standard EuroSCORE parameters could retrospectively be determined and logistic regression analysis performed. In all patients scored, creatinine clearance was calculated according to Cockcroft and Gault. The relationship between the predicted and observed 30-days mortality was evaluated in systematically selected intervals of creatinine clearance and significance values computed by employing Monte Carlo methods. Afterwards, risk scoring was performed using a continuous or a categorical value of creatinine clearance instead of serum creatinine. The predictive ability of several risk score models and the individual contribution of their predictor variables were studied using ROC curve analysis.ResultsThe comparison between the expected and observed 30-days mortalities, which were determined in different intervals of creatinine clearance, revealed the best threshold value of 55 ml/min. A significantly higher 30-days mortality was observed below this threshold and vice versa (both with p < 0.001). The local adaptation of the EuroSCORE is better than the standard EuroSCORE and was further improved by replacing serum creatinine (SC) by creatinine clearance (CC). Differential ROC analysis revealed that CC is superior to SC in providing predictive power within the logistic regression. Variable rank comparison identified CC as the best single variable predictor, even better than the variable age, former number 1, and SC, previously number 9 in the standard set of EuroSCORE variables.ConclusionThe renal function is an important determinant of mortality in heart surgery. This risk factor is not well captured in the standard EuroSCORE risk evaluation system. Our study shows that creatinine clearance, calculated according to the Cockcroft and Gault equation, should be applied to estimate the preoperative renal function instead of serum creatinine. This predictor variable replacement gains a significant improvement in the predictive accuracy of the scoring model.