Directed Search with Multiple Job Applications

We develop an equilibrium directed search model of the labor market where workers can simultaneously apply for multiple jobs. The main result is that all equilibria exhibit wage dispersion despite the fact that workers and firms are homogeneous. Wage dispersion is driven by the simultaneity of application choice. Risk-neutral workers apply for both ‘safe’ and ‘risky’ jobs. The former yield a high probability of a job offer, but for low pay, and act as a fallback option; the latter provide with higher potential payoff, but are harder to get. Furthermore, the density of posted wages is decreasing, consistent with stylized facts. Unlike most directed search models, the equilibria are not constrained efficient.

Road blocks on paleogenomes - polymerase extension profiling reveals the frequency of blocking lesions in ancient DNA

Although the last few years have seen great progress in DNA sequence retrieval from fossil specimens, some of the characteristics of ancient DNA remain poorly understood. This is particularly true for blocking lesions, i.e. chemical alterations that cannot be bypassed by DNA polymerases and thus prevent amplification and subsequent sequencing of affected molecules. Some studies have concluded that the vast majority of ancient DNA molecules carry blocking lesions, suggesting that the removal, repair or bypass of blocking lesions might dramatically increase both the time depth and geographical range of specimens available for ancient DNA analysis. However, previous studies used very indirect detection methods that did not provide conclusive estimates on the frequency of blocking lesions in endogenous ancient DNA. We developed a new method, polymerase extension profiling (PEP), that directly reveals occurrences of polymerase stalling on DNA templates. By sequencing thousands of single primer extension products using PEP methodology, we have for the first time directly identified blocking lesions in ancient DNA on a single molecule level. Although we found clear evidence for blocking lesions in three out of four ancient samples, no more than 40% of the molecules were affected in any of the samples, indicating that such modifications are far less frequent in ancient DNA than previously thought

Why Do Curly Tail Lizards (Genus Leiocephalus) Curl Their Tails? An Assessment of Displays Toward Conspecifics and Predators

Animal display behaviors are used to convey specific messages to other animals, including potential mates, rivals, and predators. However, because these different types of interactions can be mediated by a single behavioral display, or conversely, multiple signals can be used to convey one specific message, interpretation of any particular behavioral display can be difficult. Leiocephalus lizards (i.e., curly tails) provide an excellent opportunity to study the use of display behaviors across multiple contexts. Previous research has demonstrated that the use of tail curling in these lizards is associated with predation risk, but less is known regarding the use of this behavior in social interactions with conspecifics. The goal of this study was to determine the extent to which tail curling display behavior is used to mediate both social and predatory interactions in two species, Leiocephalus barahonensis and L. carinatus. We found that in lizards of both species, tail curling was used in interactions with both conspecifics and potential (human) predators. However, tail curl intensity did not differ between lizards involved in social encounters and solitary lizards, although L. barahonensis lizards performed more headbobs during social than non-social observations. Further, L. carinatus lizards exhibited greater intensity of tail curling upon fleeing from a human predator than during observations in which individuals interacted with conspecifics, and lizards that exhibited tighter tail curls fled from predators for a longer distance. Finally, tail curl intensity was not correlated with headbob displays in either species, suggesting that these two components of display communicate different information. Our results suggest that tail curling displays, while consistently a component of interactions with potential predators, are not a necessary component of social interactions. These data contribute to a more complete understanding of how and why visual signals evolve for use in communication across multiple contexts

The Evolution of Androgen Receptor Expression and Behavior in \u3cem\u3eAnolis\u3c/em\u3e Lizard Forelimb Muscles

The motor systems that produce behavioral movements are among the primary targets for the action of steroid hormones, including androgens. Androgens such as testosterone bind to androgen receptors (AR) to induce physiological changes in the size, strength, and energetic capacity of skeletal muscles, which can directly influence the performance of behaviors in which those muscles are used. Because tissues differentially express AR, resulting in tissue-specific sensitivity to androgens, AR expression may be a major target of selection for the evolution of behavior. Anolis lizards (i.e., anoles) provide a robust system for the study of androgen-regulated traits, including the behavioral traits that facilitate social display and locomotion. In this study, we examined six anole species that demonstrate significant variation in the behavioral use of the forelimbs to measure the proportion of myonuclei in the bicep muscles that express AR. Using phylogenetic comparative analyses, we found that species with a greater proportion of nuclei positive for AR expression in the biceps exhibited greater frequencies of locomotor movements and pushup displays. These results suggest that AR expression in skeletal muscles may influence the evolution of androgen-regulated behaviors in this group

Proximity effect in granular superconductor-normal metal structures

We fabricated three-dimensional disordered Pb-Cu granular structures, with various metal compositions. The typical grain size of both metals is smaller than the superconductor and normal metal coherence lengths, thus satisfying the Cooper limit. The critical temperature of the samples was measured and compared with the critical temperature of bilayers. We show how the proximity effect theories, developed for bilayers, can be modified for random mixtures and we demonstrate that our experimental data fit well the de Gennes weak coupling limit theory in the Cooper limit. Our results indicate that, in granular structures, the Cooper limit can be satisfied over a wide range of concentrations.Comment: 15 pages, 4 figure

3D Magnetic Analysis of the CMS Magnet

The CMS magnetic system consists of a super-conducting solenoid coil, 12.5 m long and 6 m free bore diameter, and of an iron flux-return yoke, which includes the central barrel, two end-caps and the ferromagnetic parts of the hadronic forward calorimeter. The magnetic flux density in the center of the solenoid is 4 T. To carry out the magnetic analysis of the CMS magnetic system, several 3D models were developed to perform magnetic field and force calculations using the Vector Fields code TOSCA. The analysis includes a study of the general field behavior, the calculation of the forces on the coil generated by small axial, radial displacements and angular tilts, the calculation of the forces on the ferromagnetic parts, the calculation of the fringe field outside the magnetic system, and a study of the field level in the chimneys for the current leads and the cryogenic lines. A procedure to reconstruct the field inside a cylindrical volume starting from the values of the magnetic flux density on the cylinder surface is considered. Special TOSCA-GEANT interface tools have being developed to input the calculated magnetic field into the detector simulation package.Comment: 4 pages, 6 figures, 1 equation, 14 reference