A partition‑based branch‑and‑bound algorithm for the project duration problem with partially renewable resources and general temporal constraints

The concept of partially renewable resources provides a general modeling framework that can be used for a wide range of different real-life applications. In this paper, we consider a resource-constrained project duration problem with partially renewable resources, where the temporal constraints between the activities are given by minimum and maximum time lags. We present a new branch-and-bound algorithm for this problem, which is based on a stepwise decomposition of the possible resource consumptions by the activities of the project. It is shown that the new approach results in a polynomially bounded depth of the enumeration tree, which is obtained by kind of a binary search. In a comprehensive experimental performance analysis, we compare our exact solution procedure with all branch-and-bound algorithms and state-of-the-art heuristics from the literature on different benchmark sets. The results of the performance study reveal that our branch-and-bound algorithm clearly outperforms all exact solution procedures. Furthermore, it is shown that our new approach dominates the state-of-the-art heuristics on well known benchmark instances

Geld rast um die Welt : der Wertpapierhandel im 21. Jahrhundert

Kaum eine andere Industrie wurde in den vergangenen beiden Jahrzehnten so massiv durch den Einzug der Informationstechnologie geprägt wie der Wertpapierhandel. Traditionelle Geschäftsmodelle haben sich grundlegend verändert. Das klassische Börsenparkett ist nahezu vollständig elektronischen Handelsplattformen gewichen

The Impact of IT-Based Trading on Securities Markets

The emergence of IT-based trading activities like algorithmic trading or high-frequency trading alters the traditional trading environment within financial markets. Thus, the question arises whether this technological arms race positively affects market quality or represents a risk related to market integrity. Within this study, we evaluate the order-to-trade-ratio for measuring overall IT-based trading activity. Furthermore, in a longitudinal study, we assess the impact of the order-to-trade-ratio on market quality. We find strong indications that price uncertainty has decreased with an increased order-to-trade-ratio and therefore has a positive impact on financial markets. However, the mere upgrade of the trading systems does not relate into increased market liquidity

The Impact of High-Frequency Trading on Modern Securities Markets

High-frequency traders account for a significant part of overall price formation and liquidity provision in modern securities markets. In order to react within microseconds, high-frequency traders depend on specialized low latency infrastructure and fast connections to exchanges, which require significant IT investments. The paper investigates a technical failure of this infrastructure at a major exchange that prevents high-frequency traders from trading at low latency. This event provides a unique opportunity to analyze the impact of high-frequency trading on securities markets. The analysis clearly shows that although the impact on trading volume and the number of trades is marginal, the effects on liquidity and to a lesser extent on price volatility are substantial when high-frequency trading is interrupted. Thus, investments in high-frequency trading technology provide positive economic spillovers to the overall market since they reduce transaction costs not only for those who invest in this technology but for all market participants by enhancing the quality of securities markets

Kostenanalyse der kurativen und palliativen Tumortherapie : (eine Stichprobenuntersuchung)

Bei weltweit steigender Inzidenz von Krebserkrankungen in Verbindung mit den beträchtlichen Kosten für die Therapie und limitierten finanziellen Ressourcen ist eine wirtschaftlich sinnvolle Verteilung der Geldmittel die erstrebenswerteste Strategie um für ein Maximum an Patienten eine den Umständen entsprechend maximal wirksame Therapieform zu ermöglichen. Zur Beurteilung der Kostenentstehung und ­verteilung bei Krebstherapien wurde eine retrospektive Analyse hinsichtlich der Dauer der verschiedenen Abschnitte der Therapie bei 30 Patienten (13 Frauen, 17 Männer) durchgeführt und die Kosten der unterschiedlichen Behandlungsabschnitte betrachtet. Am Beginn stand dabei die Frage nach der Definition der Start­ und Endpunkte der einzelnen zeitlichen Intervalle und am Schluß die Ermittlung der Kosten pro Zeiteinheit, um Vergleiche der einzelnen Therapieintervalle auf ökonomischer Basis zu ermöglichen. Dabei ergab sich schon für die relativ kleine Stichprobe mit verschiedensten Anamnesen und Therapiezeiten ein verlängertes kuratives Behandlungsintervall im Gegensatz zu einer im Vergleich kürzeren palliativen Behandlungsdauer. Dabei konnte gezeigt werden, daß die Kosten pro Behandlungstag in der Regel für die kurative Behandlung geringer ausfielen als für die palliative, wobei sich der stationäre Aufenthalt in jedem Fall als maßgeblicher Kostenfaktor herausstellte. Generell scheinen die Ergebnisse darauf hinzudeuten, daß, während sich die kurativen Kosten in gewissen Grenzen prognostizieren lassen, dies bei den palliativen Kosten so nicht vorhersagbar ist. Aufgrund der Qualität der retrospektiv gewonnenen Daten und ihrer eingeschränkten Übertragbarkeit sollte die Wertigkeit dieser Aussage jedoch auch mit der nötigen Kritik betrachtet werden

Experiments towards optical nuclear spectroscopy with thorium-229

[no abstract

Increased plasma viscosity as a reason for inappropriate erythropoietin formation

The aim of this study was to examine whether altered plasma viscosity could contribute to the inappropriately low production rate of erythropoietin (EPO) observed in patients suffering from hypergammaglobulinemias associated with multiple myeloma or Waldenström's disease. We found that the EPO formation in response to anemia in these patients was inversely related to plasma viscosity. A similar inverse relationship between plasma viscosity and EPO production was seen in rats in which EPO formation had been stimulated by exchange transfusion and the plasma viscosity of which was thereby altered by using exchange solutions of different composition to alter plasma viscosity and thus whole blood viscosity independently from hematocrit. Raising the gammaglobulin concentration to approximately 40 mg/ml plasma in the rats almost totally blunted the rise in serum EPO levels despite a fall of the hematocrit to 20%. Determination of renal EPO mRNA levels by RNase protection revealed that the reductions in serum EPO levels at higher plasma viscosities were paralleled by reductions in renal EPO mRNA levels. Taken together, our findings suggest that plasma viscosity may be a significant inhibitory modulator of anemia-induced EPO formation. The increased plasma viscosity in patients with hypergammaglobulinemias may therefore contribute to the inappropriate EPO production, which is a major reason for the anemia developing in these patients