The role of the agent's outside options in principal-agent relationships

We consider a principal-agent model of adverse selection where, in order to trade with the principal, the agent must undertake a relationship-specific investment which affects his outside option to trade, i.e. the payoff that he can obtain by trading with an alternative principal. This creates a distinction between the agent’s ex ante (before investment) and ex post (after investment) outside options to trade. We investigate the consequences of this distinction, and show that whenever an agent’s ex ante and ex post outside options differ, this may equip the principal with an additional tool for screening among different agent types, by randomizing over the probability with which trade occurs once the agent has undertaken the investment. In turn, this may enhance the efficiency of the optimal second-best contract

A dedicated haem lyase is required for the maturation of a novel bacterial cytochrome c with unconventional covalent haem binding

In bacterial c-type cytochromes, the haem cofactor is covalently attached via two cysteine residues organized in a haem c-binding motif. Here, a novel octa-haem c protein, MccA, is described that contains only seven conventional haem c-binding motifs (CXXCH), in addition to several single cysteine residues and a conserved CH signature. Mass spectrometric analysis of purified MccA from Wolinella succinogenes suggests that two of the single cysteine residues are actually part of an unprecedented CX15CH sequence involved in haem c binding. Spectroscopic characterization of MccA identified an unusual high-potential haem c with a red-shifted absorption maximum, not unlike that of certain eukaryotic cytochromes c that exceptionally bind haem via only one thioether bridge. A haem lyase gene was found to be specifically required for the maturation of MccA in W. succinogenes. Equivalent haem lyase-encoding genes belonging to either the bacterial cytochrome c biogenesis system I or II are present in the vicinity of every known mccA gene suggesting a dedicated cytochrome c maturation pathway. The results necessitate reconsideration of computer-based prediction of putative haem c-binding motifs in bacterial proteomes

Begeleiden en beoordelen van ontwerpgericht onderzoek in studio’s = Supervising and assessing design-based research in studios

In het vernieuwde vak “Educational Design Research (EDR)” van de universitaire lerarenopleiding, Master Educatie in de Bètawetenschappen werken studenten samen volgens de cyclus van EDR (McKeeney & Reeves, 2019) rondom thema’s die leven in scholen uit ons netwerk. Uit een verkennende fase, waarin praktijk en literatuur centraal staan, volgen eerste ontwerpprincipes. Het ontwerp wordt ontwikkeld en verantwoord. Ten behoeve van de implementatie en evaluatie wordt een plan gemaakt. Uit de implementatie en evaluatie volgt een eindverslag. Deze groepsproducten leiden tot een groepscijfer. Daarnaast hebben we in ons ontwerp van EDR een werkwijze ontwikkeld rondom de persoonlijke ontwikkeling van de studenten, die uiteindelijk meeweegt in de bepaling van het individuele cijfer. In deze Ontmoeting werken we aan de hand van het wereldcafé aan het bespreken van deze werkwijze; de manier waarop studiobegeleiders zowel begeleider als beoordelaar zijn; en de rol van studenten en scholen in dit geheel. Ieder onderwerp van discussie wordt aan de hand van drie opeenvolgende vragen besproken: knelpunten, oplossingen, randvoorwaarden. De opbrengst gaat in op het (door)ontwikkelen van dit proces. Daarnaast willen we andere lerarenopleidingen ondersteunen die met vergelijkbare processen werken en leren van/met deze ervaringen

Polyakov loop correlators from D0-brane interactions in bosonic string theory

In this paper we re-derive the effective Nambu-Goto theory result for the Polyakov loop correlator, starting from the free bosonic string and using a covariant quantization. The boundary conditions are those of an open string attached to two D0-branes at spatial distance R, in a target space with compact euclidean time. The one-loop free energy contains topologically distinct sectors corresponding to multiple covers of the cylinder in target space bordered by the Polyakov loops. The sector that winds once reproduces exactly the Nambu-Goto partition function. In our approach, the world-sheet duality between the open and closed channel is most evident and allows for an explicit interpretation of the free energy in terms of tree level exchange of closed strings between boundary states. Our treatment is fully consistent only in d=26; extension to generic d may be justified for large R, and is supported by Montecarlo data. At shorter scales, consistency and Montecarlo data seem to suggest the necessity of taking into account the Liouville mode of Polyakov's formulation.Comment: 17 pages, 4 figures, minor corrections, a few references added, version accepted for publication in JHE

Dynamics near the critical point: the hot renormalization group in quantum field theory

The perturbative approach to the description of long wavelength excitations at high temperature breaks down near the critical point of a second order phase transition. We study the \emph{dynamics} of these excitations in a relativistic scalar field theory at and near the critical point via a renormalization group approach at high temperature and an $\epsilon$ expansion in $d=5-\epsilon$ space-time dimensions. The long wavelength physics is determined by a non-trivial fixed point of the renormalization group. At the critical point we find that the dispersion relation and width of quasiparticles of momentum $p$ is $\omega_p \sim p^{z}$ and $\Gamma_p \sim (z-1) \omega_p$ respectively, the group velocity of quasiparticles $v_g \sim p^{z-1}$ vanishes in the long wavelength limit at the critical point. Away from the critical point for $T\gtrsim T_c$ we find $\omega_p \sim \xi^{-z}[1+(p \xi)^{2z}]^{{1/2}}$ and $\Gamma_p \sim (z-1) \omega_p \frac{(p \xi)^{2z}}{1+(p \xi)^{2z}}$ with $\xi$ the finite temperature correlation length $\xi \propto |T-T_c|^{-\nu}$. The new \emph{dynamical} exponent $z$ results from anisotropic renormalization in the spatial and time directions. For a theory with O(N) symmetry we find $z=1+ \epsilon \frac{N+2}{(N+8)^2}+\mathcal{O}(\epsilon^2)$. Critical slowing down, i.e, a vanishing width in the long-wavelength limit, and the validity of the quasiparticle picture emerge naturally from this analysis.Comment: Discussion on new dynamical universality class. To appear in Phys. Rev.

A strongly first order electroweak phase transition from strong symmetry-breaking interactions

We argue that a strongly first order electroweak phase transition is natural in the presence of strong symmetry-breaking interactions, such as technicolor. We demonstrate this using an effective linear scalar theory of the symmetry-breaking sector.Comment: LaTex, 15 pages, 3 figures in EPS format. Phys. Rev. D approved Typographically Correct version, minor grammatical change

Six-dimensional Abelian vortices with quadratic curvature self-interactions

Six-dimensional Nielsen-Olesen vortices are analyzed in the context of a quadratic gravity theory containing Euler-Gauss-Bonnet self-interactions. The relations among the string tensions can be tuned in such a way that the obtained solutions lead to warped compactification on the vortex. New regular solutions are possible in comparison with the case where the gravity action only consists of the Einstein-Hilbert term. The parameter space of the model is discussedComment: 28 pages in Latex style with 11 figure

The Path to Implementation of HIV Pre-exposure Prophylaxis for People Involved in Criminal Justice Systems

The criminal justice (CJ)-involved population in the United States (US) is among the most vulnerable to and heavily impacted by HIV. HIV prevalence is three to five times higher among incarcerated populations than in the general population and one in seven people living with HIV (PLH) pass through CJ systems each year. Among racial and ethnic minorities, HIV and incarceration are even more closely intertwined: one of every five HIV-infected black or Hispanic/Latino adults passes through CJ systems annually

Palaeoenvironmental control on distribution of crinoids in the Bathonian (Middle Jurassic) of England and France

Bulk sampling of a number of different marine and marginal marine lithofacies in the British Bathonian has allowed us to assess the palaeoenvironmental distribution of crinoids for the first time. Although remains are largely fragmentary, many species have been identified by comparison with articulated specimens from elsewhere, whilst the large and unbiased sample sizes allowed assessment of relative proportions of different taxa. Results indicate that distribution of crinoids well corresponds to particular facies. Ossicles of Chariocrinus and Balanocrinus dominate in deeper-water and lower-energy facies,with the former extending further into shallower-water facies than the latter. Isocrinus dominates in shallower water carbonate facies, accompanied by rarer comatulids, and was also present in the more marine parts of lagoons. Pentacrinites remains are abundant in very high-energy oolite shoal lithofacies. The presence of millericrinids within one, partly allochthonous lithofacies suggests the presence of an otherwise unknown hard substrate from which they have been transported. These results are compared to crinoid assemblages from other Mesozoic localities, and it is evident that the same morphological ad-aptations are present within crinoids from similar lithofacies throughout the Jurassic and Early Cretaceous