Mutually best matches

We study iterated formation of mutually best matches (IMB) in college admissions problems. When IMB produces a non-wasteful matching, the matching has many good properties like Pareto optimality and stability. Moreover, in this case IMB selects the unique core allocation and truth-telling is a Nash equilibrium for students. If preferences satisfy a single peakedness condition, or have a single crossing property, then IMB is guaranteed to produce a non-wasteful matching. These properties guarantee also that the Deferred Acceptance algorithm (DA) and the Top Trading Cycles algorithm (TTC) produce the same matching as IMB. We compare these results with some well-known results about when DA is Pareto optimal, or when DA and TTC produce the same matching. </p

From pairs of most similar sequences to phylogenetic best matches

Background Many of the commonly used methods for orthology detection start from mutually most similar pairs of genes (reciprocal best hits) as an approximation for evolutionary most closely related pairs of genes (reciprocal best matches). This approximation of best matches by best hits becomes exact for ultrametric dissimilarities, i.e., under the Molecular Clock Hypothesis. It fails, however, whenever there are large lineage specific rate variations among paralogous genes. In practice, this introduces a high level of noise into the input data for best-hit-based orthology detection methods. Results If additive distances between genes are known, then evolutionary most closely related pairs can be identified by considering certain quartets of genes provided that in each quartet the outgroup relative to the remaining three genes is known. A priori knowledge of underlying species phylogeny greatly facilitates the identification of the required outgroup. Although the workflow remains a heuristic since the correct outgroup cannot be determined reliably in all cases, simulations with lineage specific biases and rate asymmetries show that nearly perfect results can be achieved. In a realistic setting, where distances data have to be estimated from sequence data and hence are noisy, it is still possible to obtain highly accurate sets of best matches. Conclusion Improvements of tree-free orthology assessment methods can be expected from a combination of the accurate inference of best matches reported here and recent mathematical advances in the understanding of (reciprocal) best match graphs and orthology relations. Availability Accompanying software is available at https://github.com/david-schaller/AsymmeTree

Competition and Resource Sensitivity in Marriage and Roommate Markets

We consider one-to-one matching markets in which agents can either be matched as pairs or remain single. In these so-called roommate markets agents are consumers and resources at the same time. We investigate two new properties that capture the effect a newcomer has on incumbent agents. Competition sensitivity focuses on the newcomer as additional consumer and requires that some incumbents will suffer if competition is caused by a newcomer. Resource sensitivity focuses on the newcomer as additional resource and requires that this is beneficial for some incumbents. For solvable roommate markets, we provide the first characterizations of the core using either competition or resource sensitivity. On the class of all roommate markets, we obtain two associated impossibility results.microeconomics ;

Competition and Resource Sensitivity in Marriage and Roommate Markets

We consider one-to-one matching markets in which agents can either be matched as pairs or remain single. In these so-called roommate markets agents are consumers and resources at the same time. We investigate two new properties that capture the effect a newcomer has on incumbent agents. Competition sensitivity focuses on the newcomer as additional consumer and requires that some incumbents will suffer if competition is caused by a newcomer. Resource sensitivity focuses on the newcomer as additional resource and requires that this is beneficial for some incumbents. For solvable roommate markets, we provide the first characterizations of the core using either competition or resource sensitivity. On the domain of all roommate markets, we obtain two associated impossibility results.Core, Matching, Competition Sensitivity, Resource Sensitivity, Roommate Market.

Competition and Resource Sensitivity in Marriage and Roommate Markets

We consider one-to-one matching markets in which agents can either be matched as pairs or remain single. In these so-called roommate markets agents are consumers and resources at the same time. We investigate two new properties that capture the effect newcomers have on incumbent agents. Competition sensitivity focuses on newcomers as additional consumers and requires that some incumbents will suffer if competition is caused by newcomers. Resource sensitivity focuses on newcomers as additional resources and requires that this is beneficial for some incumbents. For solvable roommate markets, we provide the first characterizations of the core using either competition or resource sensitivity. On the domain of all roommate markets, we obtain two associated impossibility results.core; matching; competition sensitivity; resource sensitivity; roommate market

Incentive Contracts and Efficient Unemployment Benefits

Several European countries have reformed their labor market institutions. Incentive effects of unemployment benefits have been an important aspect of these reforms. We analyze this issue in a principal-agent model, focusing on unemployment levels and labor productivity. In our model, a higher level of unemployment benefits improves the worker's position in wage bargaining, leading to stronger effort incentives and higher output. However, it also reduces incentives for labor market participation. Accordingly, there is a trade-off. We analyze how changes in the economic environment such as globalization and better educated workers affect this trade-off.Unemployment benefits, incentive contracts, Nash bargaining, moral hazard, globalisation

Sequencing and analysis of the gastrula transcriptome of the brittle star Ophiocoma wendtii

Background The gastrula stage represents the point in development at which the three primary germ layers diverge. At this point the gene regulatory networks that specify the germ layers are established and the genes that define the differentiated states of the tissues have begun to be activated. These networks have been well-characterized in sea urchins, but not in other echinoderms. Embryos of the brittle star Ophiocoma wendtii share a number of developmental features with sea urchin embryos, including the ingression of mesenchyme cells that give rise to an embryonic skeleton. Notable differences are that no micromeres are formed during cleavage divisions and no pigment cells are formed during development to the pluteus larval stage. More subtle changes in timing of developmental events also occur. To explore the molecular basis for the similarities and differences between these two echinoderms, we have sequenced and characterized the gastrula transcriptome of O. wendtii. Methods Development of Ophiocoma wendtii embryos was characterized and RNA was isolated from the gastrula stage. A transcriptome data base was generated from this RNA and was analyzed using a variety of methods to identify transcripts expressed and to compare those transcripts to those expressed at the gastrula stage in other organisms. Results Using existing databases, we identified brittle star transcripts that correspond to 3,385 genes, including 1,863 genes shared with the sea urchin Strongylocentrotus purpuratus gastrula transcriptome. We characterized the functional classes of genes present in the transcriptome and compared them to those found in this sea urchin. We then examined those members of the germ-layer specific gene regulatory networks (GRNs) of S. purpuratus that are expressed in the O. wendtii gastrula. Our results indicate that there is a shared ‘genetic toolkit’ central to the echinoderm gastrula, a key stage in embryonic development, though there are also differences that reflect changes in developmental processes. Conclusions The brittle star expresses genes representing all functional classes at the gastrula stage. Brittle stars and sea urchins have comparable numbers of each class of genes and share many of the genes expressed at gastrulation. Examination of the brittle star genes in which sea urchin orthologs are utilized in germ layer specification reveals a relatively higher level of conservation of key regulatory components compared to the overall transcriptome. We also identify genes that were either lost or whose temporal expression has diverged from that of sea urchins