Philanthropically Funded Heroism Awards for Kidney Donors?

Denna rapport är den andra av två delarbeten (det tidigare publicerades i samma rapportserie 2004) som är ett resultat av ett samarbete mellan Centrum för utvärdering av medicinsk teknologi och Landstinget i Östergötland. Målet har varit att utveckla beslutsunderlaget för öppna horisontella prioriteringar inom landstinget i Östergötland genom att fördela alla kostnader för sjukdom och ohälsa på olika sjukdomsgrupper. Vi som har arbetat med denna rapport är Andrea Schmidt, hälsoekonom vid CMT, Institutionen för medicin och hälsa (IMH) samt Agneta Andersson, Fil Dr, forskare vid Socialmedicin och folkhälsovetenskap (IMH) samt FoU-handledare vid FoU-enheten för Närsjukvård vid Landstinget i Östergötland. Vi vill rikta ett stort tack till Lars Svensson, Rolf Wiklund samt Bengt Grip, KPP-gruppen vid Landstinget i Östergötland. Utan er hjälp och bistånd med data hade detta projekt inte varit genomförbart. Linköping 2007 Andrea Schmidt           Agneta Andersso

Unraveling Reduces the Scope of an Entry Level Labor Market: Gastroenterology With and Without a Centralized Match

From 1986 through 1997 the entry-level market for American gastroenterologists was organized by a centralized clearinghouse. Before, and since, it has been conducted via a decentralized market in which appointment dates have unraveled to well over a year before the start of employment. The career paths of gastroenterologists therefore offer a unique opportunity to examine the difference between the market when appointments are decentralized and early, versus when they are made later via a centralized clearinghouse. (Most centralized clearinghouses remain in use once established, and so there is no way to separate changes due to the clearinghouse from other changes that may have taken place over time.) We find that, both before and after the years in which the centralized clearinghouse was used, gastroenterologists are less mobile, and more likely to be employed at the same hospital in which they were internal medicine residents, than when the clearinghouse was in use. This suggests that the clearinghouse serves not only to coordinate the timing of appointments, but that it also increases the scope of the market, compared to decentralized markets with early appointments and exploding offers. This has implications for theories of market failure due to unraveling over time.

Market Culture: How Norms Governing Exploding Offers Affect Market Performance

Many markets have organizations that influence or try to establish norms concerning when offers can be made, accepted and rejected. Examining a dozen previously studied markets suggests that markets in which transactions are made far in advance are markets in which it is acceptable for firms to make exploding offers, and unacceptable for workers to renege on commitments they make, however early. But this evidence is only suggestive, because the markets differ in many ways other than norms concerning offers. Laboratory experiments allow us to isolate the effects of exploding offers and binding acceptances. In a simple environment, in which uncertainty about applicants' quality is resolved over time, we find inefficient early contracting when firms can make exploding offers and applicants' acceptances are binding. Relaxing either of these two conditions causes matching to take place later, when more information about applicants' qualities is available, and consequently results in higher efficiency and fewer blocking pairs. This suggests that elements of market culture may play an important role in influencing market performance.

On the Relationship between Transmission Power and Capacity of an Underwater Acoustic Communication Channel

The underwater acoustic channel is characterized by a path loss that depends not only on the transmission distance, but also on the signal frequency. As a consequence, transmission bandwidth depends on the transmission distance, a feature that distinguishes an underwater acoustic system from a terrestrial radio system. The exact relationship between power, transmission band, distance and capacity for the Gaussian noise scenario is a complicated one. This work provides a closed-form approximate model for 1) power consumption, 2) band-edge frequency and 3) bandwidth as functions of distance and capacity required for a data link. This approximate model is obtained by numerical evaluation of analytical results which takes into account physical models of acoustic propagation loss and ambient noise. The closed-form approximations may become useful tools in the design and analysis of underwater acoustic networks.Comment: 6 pages, 9 Figures, Awaiting acceptance to IEEE Oceans 08 (Conference), Kobe, Japa

Broadcasting in Time-Division Duplexing: A Random Linear Network Coding Approach

We study random linear network coding for broadcasting in time division duplexing channels. We assume a packet erasure channel with nodes that cannot transmit and receive information simultaneously. The sender transmits coded data packets back-to-back before stopping to wait for the receivers to acknowledge the number of degrees of freedom, if any, that are required to decode correctly the information. We study the mean time to complete the transmission of a block of packets to all receivers. We also present a bound on the number of stops to wait for acknowledgement in order to complete transmission with probability at least $1-\epsilon$, for any $\epsilon>0$. We present analysis and numerical results showing that our scheme outperforms optimal scheduling policies for broadcast, in terms of the mean completion time. We provide a simple heuristic to compute the number of coded packets to be sent before stopping that achieves close to optimal performance with the advantage of a considerable reduction in the search time.Comment: 6 pages, 5 figures, Submitted to Workshop on Network Coding, Theory, and Applications (NetCod 2009

Whether and Where to Code in the Wireless Relay Channel

The throughput benefits of random linear network codes have been studied extensively for wirelined and wireless erasure networks. It is often assumed that all nodes within a network perform coding operations. In energy-constrained systems, however, coding subgraphs should be chosen to control the number of coding nodes while maintaining throughput. In this paper, we explore the strategic use of network coding in the wireless packet erasure relay channel according to both throughput and energy metrics. In the relay channel, a single source communicates to a single sink through the aid of a half-duplex relay. The fluid flow model is used to describe the case where both the source and the relay are coding, and Markov chain models are proposed to describe packet evolution if only the source or only the relay is coding. In addition to transmission energy, we take into account coding and reception energies. We show that coding at the relay alone while operating in a rateless fashion is neither throughput nor energy efficient. Given a set of system parameters, our analysis determines the optimal amount of time the relay should participate in the transmission, and where coding should be performed.Comment: 11 pages, 12 figures, to be published in the IEEE JSAC Special Issue on Theories and Methods for Advanced Wireless Relay

Random Linear Network Coding For Time Division Duplexing: Energy Analysis

We study the energy performance of random linear network coding for time division duplexing channels. We assume a packet erasure channel with nodes that cannot transmit and receive information simultaneously. The sender transmits coded data packets back-to-back before stopping to wait for the receiver to acknowledge the number of degrees of freedom, if any, that are required to decode correctly the information. Our analysis shows that, in terms of mean energy consumed, there is an optimal number of coded data packets to send before stopping to listen. This number depends on the energy needed to transmit each coded packet and the acknowledgment (ACK), probabilities of packet and ACK erasure, and the number of degrees of freedom that the receiver requires to decode the data. We show that its energy performance is superior to that of a full-duplex system. We also study the performance of our scheme when the number of coded packets is chosen to minimize the mean time to complete transmission as in [1]. Energy performance under this optimization criterion is found to be close to optimal, thus providing a good trade-off between energy and time required to complete transmissions.Comment: 5 pages, 6 figures, Accepted to ICC 200