"Download for Free" - When Do Providers of Digital Goods Offer Free Samples?

In a monopoly setting where consumers cannot observe the quality of the product we show that free samples which are of a lower quality than the marketed digital goods are used together with high prices as signals for a superior quality if the number of informed consumers is small and if the difference between the high and the low quality is not too small. Social welfare is higher, if the monopolist uses also free samples as signals, compared to a situation where he is restricted to pure price signalling. Both, the monopolist and consumers benefit from the additional signal.Digital Goods; Free Samples; Multi-dimensional Signalling

"Download for Free": When do providers of digital goods offer free samples?

In a monopoly setting where consumers cannot observe the quality of the product we show that free samples which are of a lower quality than the marketed digital goods are used together with high prices as signals for a superior quality if the number of informed consumers is small and if the difference between the high and the low quality is not too small. Social welfare is higher, if the monopolist uses also free samples as signals, compared to a situation where he is restricted to pure price signalling. Both, the monopolist and consumers benefit from the additional signal. --

Identification of left ventricular model parameters

Simulations with a model of left ventricular pressure generation consisting of time-varying elastance, resistance, series-elastance, and deactivation were fitted to pressure curves measured in the isolated rabbit ventricle. For constant ejection flows, a fit with a RMS error of 2.78 mmHg was obtained provided that deactivation was actually incorporated in the model. Deactivation was assumed to depend linearly on end ejection pressure. Resistance was found to be independent of volum

Left ventricular force-velocity relations measured from quick volume changes

Left ventricles of rabbit hearts were subjected to series of quick volume releases (QVR) — taking placw within 6 ms — applied at fixed times in the cardiac cycle. The hearts were paced artificially and allowed to contract isovolumically. The QVR was used as a tool for realizing predetermined pressure values at any time during the ascending limb of the intra-ventricular pressure curve. Any desired pressure could be attained by suitable choice of the QVR amplitude. By relatingdP/dt values occuring immediately after the QVR to the pressure attained by the QVR for different QVR amplitudes, instantaneousdP/dt relations were obtained. Time effects on these relations were studied by repeating the QVR series with increasing amplitudes at different but constant times. Influences of volume and contractile state were examined by varying end diastolic pressure (EDP) and the perfusate [Ca2+]. The data were fitted with adP/dt-P relation derived from the Hill equation using a simple geometric model of the ventricle and a two element model of the myocardium. The experimental relations were described adequately by the model. The parameters in the Hill equation estimated for heart muscle were compared to those previously reported on heart muscle experiments. Parameter values obtained were:a/F0: 0.001–1.3;F0 (mean maximal force forVCE=0): 12.2-3.5 N;b: 1.7–13.2 cm/s.F0 rises at the beginning of systole and shows a plateau from ca. 60–100% time of peak pressure. This time course was influenced by changes in EDP and [Ca2+]. Parameterb exhibits a time course comparable to that of ventricular pressure. It was not influenced by EDP changes and only slightly increased by an increase in [Ca2+]

Deactivation in the rabbit left ventricle induced by constant ejection flow

A study of pressure generated by the left ventricle after ejection with constant flow for different values of the ejection flow, flow duration, time of flow arrest, and ventricular volume is discussed. It was found that pressure after ejection, normalized with respect to isovolumic pressure, is regenerated according to a model consisting of an elastance, a resistance, a series elastance, and an additional deactivation component. Deactivation is defined as the difference between the value 1 and the plateau value of the normalized pressure after constant flow ejection. It is shown that this plateau value is constant after constant flow ejection until the minimum in isovolumic dP/dt, i.e. during physiological systole. The plateau value is uniquely related to the value of the normalized pressure with a time constant of 10.44±0.09 ms which agrees with the series-elastance time constant of 10.35±0.26 m

Restructuring Electricity Markets when Demand is Uncertain: Effects on Capacity Investments, Prices and Welfare

We examine the effects of restructuring electricity markets on capacity investments, retail prices and welfare when demand is uncertain. We study the following market configurations: (i) integrated monopoly, (ii) integrated duopoly with wholesale trade, and (iii) separated duopoly with wholesale trade. Assuming that wholesale prices can react to changes in retail prices (but not vice versa), we find that generators install sufficient capacity to serve retail demand in each market configuration, thus avoiding blackouts. Furthermore, aggregate capacity levels and retail prices are such that the separated (integrated) duopoly with wholesale trade performs best (worst) in terms of welfare.electricity; investments; generating capacities; vertical integration; monopoly and competition

A model of the electrical behaviour of myelinated sensory nerve fibres based on human data

Calculation of the response of human myelinated sensory nerve fibres to spinal cord stimulation initiated the development of a fibre model based on electro-physiological and morphometric data for human sensory nerve fibres. The model encompasses a mathematical description of the kinetics of the nodal membrane, and a non-linear fibre geometry. Fine tuning of only a few, not well-established parameters was performed by fitting the shape of a propagating action potential and its diameter-dependent propagation velocity. The quantitative behaviour of this model corresponds better to experimentally determined human fibre properties than other mammalian, non-human models do. Typical characteristics, such as the shape of the action potential, the propagation velocity and the strength-duration behaviour show a good fit with experimental data. The introduced diameter-dependent parameters did not result in a noticeable diameter dependency of action potential duration and refractory period. The presented model provides an improved tool to analyse the electrical behaviour of human myelinated sensory nerve fibres