Hydrodynamic simulations of captured protoatmospheres around Earth-like planets

Young terrestrial planets, when they are still embedded in a circumstellar disk, accumulate an atmosphere of nebula gas. The evolution and eventual evaporation of the protoplanetary disk affect the structure and dynamics of the planetary atmosphere. These processes, combined with other mass loss mechanisms, such as thermal escape driven by extreme ultraviolet and soft X-ray radiation (XUV) from the young host star, determine how much of the primary atmosphere, if anything at all, survives into later stages of planetary evolution. Our aim is to explore the structure and the dynamic outflow processes of nebula-accreted atmospheres in dependency on changes in the planetary environment. We integrate stationary hydrostatic models and perform time-dependent dynamical simulations to investigate the effect of a changing nebula environment on the atmospheric structure and the timescales on which the protoatmosphere reacts to these changes. We find that the behavior of the atmospheres strongly depends on the mass of the planetary core. For planets of about Mars-mass the atmospheric structure, and in particular the atmospheric mass, changes drastically and on very short timescales whereas atmospheres around higher mass planets are much more robust and inert

Fairness and Contract Design

We show experimentally that fairness concerns may have a decisive impact on the actual and optimal choice of contracts in a moral hazard context. Bonus contracts that offer a voluntary and unenforceable bonus for satisfactory performance provide powerful incentives and are superior to explicit incentive contracts when there are some fair-minded players. But trust contracts that pay a generous wage upfront are less efficient than incentive contracts. The principals understand this and predominantly choose the bonus contracts. Our results are consistent with recently developed theories of fairness, which offer important new insights into the interaction of contract choices, fairness and incentives

Contracts, Fairness, and Incentives

We show experimentally that fairness concerns may have a decisive impact on both the actual and the optimal choice of contracts in a moral hazard context. Explicit incentive contracts that are optimal according to self-interest theory become inferior when some agents value fairness. Conversely, implicit bonus contracts that are doomed to fail among purely selfish actors provide powerful incentives and become superior when there are some fair-minded players. The principals understand this and predominantly choose the bonus contracts, even preferring a pure bonus contract over a contract that combines the enforcement power of explicit and implicit incentives. This contract preference is associated with the fact that explicit incentives weaken the enforcement power of implicit bonus incentives significantly. Our results are largely consistent with recently developed theories of fairness, which also offer interesting new insights into the interaction of contract choices, fairness and incentives.moral hazard, incentives, bonus contract, fairness, inequity aversion

Simple Modifications of Branched PEI Lead to Highly Efficient siRNA Carriers with Low Toxicity

Polymer carriers like PEI which proved their efficiency in DNA delivery were found to be far less effective for the applications with siRNA. In the current study, we generated a number of nontoxic derivates of branched PEI through modification of amines by ethyl acrylate, acetylation of primary amines, or introduction of negatively charged propionic acid or succinic acid groups to the polymer structure. The resulting products showed high efficiency in siRNA-mediated knockdown of target gene. In particular, succinylation of branched PEI resulted in up to 10-fold lower polymer toxicity in comparison to unmodified PEI. Formulations of siRNA with succinylated PEI were able to induce remarkable knockdown (80% relative to untreated cells) of target luciferase gene at the lowest tested siRNA concentration of 50 nM in Neuro2ALuc cells. The polyplex stability assay revealed that the efficiency of formulations which are stable in physiological saline is independent of the affinity of siRNA to the polymer chain. The improved properties of modified PEI as siRNA carrier are largely a consequence of the lower polymer toxicity. In order to achieve significant knockdown of target gene, the PEI-based polymer has to be applied at higher concentrations, required most probably for sufficient accumulation and proton sponge effects in endosomes. Unmodified PEI is highly toxic at such polymer concentrations. In contrast, the far less toxic modified analogues can be applied in concentrations required for the knockdown of target genes without side effects

Fairness, Incentives and Contractual Incompleteness

We show that concerns for fairness may have dramatic consequences for the optimal provision of incentives in a moral hazard context. Incentive contracts that are optimal when there are only selfish actors become inferior when some agents are concerned about fairness. Conversely, contracts that are doomed to fail when there are only selfish actors provide powerful incentives and become superior when there are also fair-minded players. These predictions are strongly supported by the results of a series of experiments. Furthermore, our results suggest that the existence of fair actors may be an important reason why many contracts are left deliberately incomplete.Incentive contracts, moral hazard, fairness, reciprocity, incomplete contracts

Contracts, Fairness, and Incentives

We show experimentally that fairness concerns may have a decisive impact on both the actual and the optimal choice of contracts in a moral hazard context. Explicit incentive contracts that are optimal according to self-interest theory become inferior when some agents value fairness. Conversely, implicit bonus contracts that are doomed to fail among purely selfish actors provide powerful incentives and become superior when there are some fair-minded players. The principals understand this and predominantly choose the bonus contracts, even preferring a pure bonus contract over a contract that combines the enforcement power of explicit and implicit incentives. This contract preference is associated with the fact that explicit incentives weaken the enforcement power of implicit bonus incentives significantly. Our results are largely consistent with recently developed theories of fairness, which also offer interesting new insights into the interaction of contract choices, fairness and incentives.Moral Hazard; Incentives; Bonus Contract; Fairness; Inequity Aversion

John Andrew Jackson: Enslaved Resistance, Uncle Tom’s Cabin, and the Downfall of American Chattel Slavery

John Andrew Jackson was a former slave who lived in the early-to-middle nineteenth century. After escaping slavery in South Carolina and making his way north to Massachusetts, Jackson was forced to head to Canada after the passing of the Fugitive Slave Act. Jackson lectured about his experiences as a slave after he travelled to England and he eventually returned to South Carolina after the Civil War, to the place where he was enslaved, where he worked to improve the lives of other former slaves. During his journey to Canada Jackson met Harriet Beecher Stowe, who housed Jackson and helped him escape the United States. Jackson was likely the first slave Stowe housed and Jackson describes their interaction in his memoir, The Experience of a Slave in South Carolina. Jackson told Stowe his story, and many of the events and themes Jackson spoke of in his memoir—and likely told Stowe about—have parallels to Uncle Tom’s Cabin, one of the most influential books in American History. Who was John Andrew Jackson, and what do his life and experiences reveal about American slavery and the historical context in which he lived? In this paper I will argue that Jackson provides a specific example of how enslaved African Americans, their activism, narratives, and resistance, were critical in the creation of the circumstances leading to the downfall of chattel slavery in America

Fairness and Contract Design

We show experimentally that fairness concerns may have a decisive impact on the actual and optimal choice of contracts in a moral hazard context. Bonus contracts that offer a voluntary and unenforceable bonus for satisfactory performance provide powerful incentives and are superior to explicit incentive contracts when there are some fair-minded players. But trust contracts that pay a generous wage upfront are less efficient than incentive contracts. The principals understand this and predominantly choose the bonus contracts. Our results are consistent with recently developed theories of fairness, which offer important new insights into the interaction of contract choices, fairness and incentives.Moral Hazard; Incentives; Bonus Contract; Trust Contract; Fairness; Inequity Aversion