An International Pooled Analysis for Obtaining a Benchmark Dose for Environmental Lead Exposure in Children

Lead is a recognized neurotoxicant, but estimating effects at the lowest measurable levels is difficult. An international pooled analysis of data from seven cohort studies reported an inverse and supra‐linear relationship between blood lead concentrations and IQ scores in children. The lack of a clear threshold presents a challenge to the identification of an acceptable level of exposure. The benchmark dose (BMD) is defined as the dose that leads to a specific known loss. As an alternative to elusive thresholds, the BMD is being used increasingly by regulatory authorities. Using the pooled data, this article presents BMD results and applies different statistical techniques in the analysis of multistudy data. The calculations showed only a limited variation between studies in the steepness of the dose‐response functions. BMD results were quite robust to modeling assumptions with the best fitting models yielding lower confidence limits (BMDLs) of about 0.1–1.0 μ g/dL for the dose leading to a loss of one IQ point. We conclude that current allowable blood lead concentrations need to be lowered and further prevention efforts are needed to protect children from lead toxicity.     

Determinanten des Informationsgehalts von Managementprognosen – eine empirische Untersuchung anhand der DAX und MDAX-Unternehmen

In this article the characteristics and determinants of the information content of management earnings forecasts of the German DAX and MDAX companies between 2002 and 2005 are analyzed. As proxy for the information content I use the precision of the wording of a forecast. I can show that the forecasts of MDAX companies are more precisely formulated than those of DAX companies. Furthermore forecasts are formulated more precisely, when companies have, (1) a lower percentage of intangible assets, (2) lower market capitalization, (3) lower volatility of earnings and (4) a higher need for external financing.     

Estimating a frequency distribution when the sampling is biased

A simple random sample on a random variable A allows its density to be consistently estimated, by a histogram or preferably a kernel density estimate. When the sampling is biased towards certain x-values these methods instead estimate a weighted version of the density function. This article proposes a method for estimating both the density and the sampling bias simultaneously. The technique requires two independent samples and utilises ideas from mark-recapture experiments. An estimator of the size of the sampled population also follows simply from this density estimate.     

Modellgestützte Flexibilitätsanalyse von Strategien zur Ersatzteilversorgung in der Nachserienphase

An important task in after sales service is the provision of spare parts for durables. Due to its nature and dependence on earlier sales, the demand for spare parts is inherently dynamic and uncertain requiring for high procurement flexibility. During the product life cycle, inventory management of spare parts is performed efficiently under use of flexibility provided by existing production facilities. This situation completely changes once the OEM ceases production of the parent product. A prime option of procuring spare parts for the End-of-production period is to place a final order for parts when regular production ends. Besides low unit production costs, this option does not contain any flexibility, yielding a high risk of obsolescence of stored parts, and at the same time a high risk of not being able to satisfy all demand during the service period. In order to increase flexibility further options like extra production at higher unit cost or remanufacturing of components taken from used products could be used. After introducing the problem and a basic quantitative model, we evaluate flexibility properties of strategies using different combinations of the above options. In doing so we distinguish between quantity, time, and stock related flexibility. In a comprehensive numerical study it is investigated to which extent flexibility properties of the different strategies can contribute to their economic profitability.     

Hierarchische Planung für industrielle Logistikdienstleister

In this paper a planning and control system for logistics service providers (called LPS system) is developed under consideration of their specific flexibility potentials. Due to the complexity of such planning decisions (different planning levels and data quality of these levels as well as time horizons etc.), a multi-stage, hierarchical planning system is proposed which minimizes the relevant costs under consideration of the flexibilities. The advantage of a hierarchical planning concept consists in a limited planning complexity because otherwise data collection and solution development would lead to unsolvable problems in practice. The results of using LPS systems for a real-life case show a significant pay-off for logistics service providers due to the remarkable cost savings by applying a hierarchical planning concept.     

String decomposition of full-period tausworthe sequences

Because of their nice properties relative to the frequency of occurrence of n-tuples, Tausworthe sequences have been used frequently in recent years as the basis for random number generators. This paper describes a similar result relative to the frequency of occurrence of maximal-length strings of like bits. In particular, for any full-period Tausworthe sequence, the distribution of string lengths is precisely equal to the expected distribution of string lengths for a truly random bit sequence of comparable size.     

Leitung mit Supervisionskompetenz

The author describes a position of a supervisor in a clinical institution, which he would have rejected some years ago??to adopt a management role as supervisor and to act mainly in the role of a supervisor. But the recent experiences have shown, that this may be possible and successful. This is illustrated by a case study.