Complementary Platforms

We introduce an analytical framework close to the canonical model of platform competition investigated by Rochet and Tirole (2006) to study pricing decisions in two-sided markets when two or more platforms are needed simultaneously for the successful completion of a transaction. The model developed is a natural extension of the Cournot-Ellet theory of complementary monopoly featuring clear cut asymmetric single- and multihoming patterns across the market. The results indicate that the so-called anticommons problem generalizes to two-sided markets because individual platforms do not take into account the negative pricing externality they exert on the other platforms. As a result, mergers between such platforms may be welfare enhancing, but involve redistribution of surplus from one side of the market to the other. Moreover, the limit of an atomistic allocation of property rights however is not monopoly pricing, indicating that there also exist differences with the received theory of complementarity

Pulmonary Angiograms and Isotope Lung Scans — Their Role in the Diagnosis of Pulmonary Embolism

Experience gained in the study of 307 patients by pulmonary angiograms and/or isotope lung scans has led to concepts regarding the limitation and usefulness of each. The scan is ideally useful when the patient with suspected pulmonary embolism has a negative chest film. Angiograms should be performed when there are parenchymal infiltrations on the chest radiograph or when a definite diagnosis is necessary. Either study should be performed early in the course of the patient\u27s illness to permit diagnostic study