Evidence of fast pebble growth near condensation fronts in the HL Tau protoplanetary disk

Water and simple organic molecular ices dominate the mass of solid materials available for planetesimal and planet formation beyond the water snow line. Here we analyze ALMA long baseline 2.9, 1.3 and 0.87 mm continuum images of the young star HL Tau, and suggest that the emission dips observed are due to rapid pebble growth around the condensation fronts of abundant volatile species. Specifically, we show that the prominent innermost dip at 13 AU is spatially resolved in the 0.87 mm image, and its center radius is coincident with the expected mid-plane condensation front of water ice. In addition, two other prominent dips, at distances of 32 and 63 AU, cover the mid-plane condensation fronts of pure ammonia or ammonia hydrates and clathrate hydrates (especially with CO and N$_2$) formed from amorphous water ice. The spectral index map of HL Tau between 1.3 and 0.87 mm shows that the flux ratios inside the dips are statistically larger than those of nearby regions in the disk. This variation can be explained by a model with two dust populations, where most of solid mass resides in a component that has grown into decimeter size scales inside the dips. Such growth is in accord with recent numerical simulations of volatile condensation, dust coagulation and settling.Comment: 6 pages, 3 figures, Accepted for publication in the Astrophysical Journal Letter

Brothers in Arms - An Experiment on the Alliance Puzzle

Our experimental analysis of alliances in conflicts leads to three main findings. First, even in the absence of repeated interaction, direct contact or communication, free-riding among alliance members is far less pronounced than what would be expected from non-cooperative theory. Second, this possible solidarity among ‘brothers in arms’ when fighting against an outside enemy may rapidly deteriorate or disappear as soon as the outside enemy disappears. Third, when fighting an outside enemy, ‘brothers in arms’ may already anticipate future internal conflict about dividing the spoils of winning; however, this subsequent internal conflict does not discourage alliance members from expending much effort in the contest against the external enemy.alliance, conflict, contest, free-riding, hold-up problem, solidarity

The Impact of State Taxes on Self-Insurance

This paper assesses whether insurers' state taxes reduce purchases of property-casualty coverage. Tests are conducted using state aggregates of insurer-level data from publicly-available, annual accounting reports for 1993, 1994, and 1995. A positive relation between self-insurance and state taxes is detected, consistent with consumers opting to self-insure rather than bear the incidence of higher insurer taxes. The primary empirical estimates imply that a 1 percent increase in the state premium tax rate reduces non-automobile insured losses by 0.18 percent to 0.28 percent. These elasticities suggest that for the mean state, a standard deviation increase in the state tax rate (0.5 percent) would lower insured losses by approximately $140 million or 7.5 percent of current coverage. As expected, tax effects vary with the elasticity of demand. When demand is largely inelastic, e.g., automobile liability coverage, taxes do not affect self-insurance.

Value stability and change during self-chosen life transitions: Self-selection versus socialization effects

Copyright @ 2013 APA. This article may not exactly replicate the final version published in the APA journal. It is not the copy of record.Three longitudinal studies examine a fundamental question regarding adjustment of personal values to self-chosen life transitions: Do values fit the new life setting already at its onset, implying value-based self-selection? Or do values change to better fit the appropriate and desirable values in the setting, implying value socialization? As people are likely to choose a life transition partly based on their values, their values may fit the new life situation already at its onset, leaving little need for value socialization. However, we propose that this may vary as a function of the extent of change the life transition entails, with greater change requiring more value socialization. To enable generalization, we used 3 longitudinal studies spanning 3 different life transitions and different extents of life changes: vocational training (of new police recruits), education (psychology vs. business students), and migration (from Poland to Britain). Although each life transition involved different key values and different populations, across all 3 studies we found value fit to the life situation already early in the transition. Value socialization became more evident the more aspects of life changed as part of the transition, that is, in the migration transition. The discussion focuses on the implications of these findings for research on values and personality change, as well as limitations and future directions for research

The infrared spectra of ABC-stacking tri- and tetra-layer graphenes studied by first-principles calculations

The infrared absorption spectra of ABC-stacking tri- and tetra-layer graphenes are studied using the density functional theory. It is found that they exhibit very different characteristic peaks compared with those of AB-stacking ones, caused by the different stacking sequence and interlayer coupling. The anisotropy of the spectra with respect to the direction of the light electric field is significant. The spectra are more sensitive to the stacking number when the electric field is perpendicular to the graphene plane due to the interlayer polarization. The high sensitivities make it possible to identify the stacking sequence and stacking number of samples by comparing theory and experiment.Comment: 7 pages, 5 figure

Brothers in arms: An experiment on the alliance puzzle

Our experimental analysis of alliances in conflicts leads to three main findings. First, even in the absence of repeated interaction, direct contact or communication, free-riding among alliance members is far less pronounced than what would be expected from non-cooperative theory. Second, this possible solidarity among brothers in arms when fighting against an outside enemy may rapidly deteriorate or disappear as soon as the outside enemy disappears. Third, when fighting an outside enemy, brothers in arms may already anticipate future internal conflict about dividing the spoils of winning; however, this subsequent internal conflict does not discourage alliance members from expending much effort in the contest against the external enemy. -- Unsere experimentelle Studie zu Allianzen in Konflikten führt zu drei Hauptergebnissen. Selbst ohne wiederholte Interaktion, direkten Kontakt oder Kommunikation zwischen den Teilnehmern ist das Trittbrettfahren der Mitglieder der Allianz viel weniger stark ausgeprägt, als es die nicht-kooperative Theorie erwarten lassen würde. Diese Solidarität zwischen den Kampfgefährten, die im Wettbewerb mit einem Außenstehenden zu beobachten ist, nimmt jedoch rapide ab, sobald der Gegner verschwunden ist. Im Kampf mit dem externen Gegner können die Kampfgefährten bereits damit rechnen, dass es zu einem internen Konflikt über die Aufteilung der Kriegsbeute kommen wird; dieser folgende interne Verteilungskonflikt hält die Mitglieder der Allianz jedoch nicht davon ab, einen hohen Einsatz im Kampf mit dem externen Gegner zu leisten.Alliance,conflict,contest,free-riding,hold-up problem,solidarity