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Punishment regulates selfish behaviors and maintains cooperation. However, because punishment imposes costs on another person, it could also harm relationships. The current work asked how punishment shapes 5- to 10-year-olds' (Study 1; n=128) and adults' (Study 2; n=159) attitudes toward punishers and those who receive punishment as well as their inferences about relationships between punishers and targets. We reasoned that the motives underlying punishment might shape evaluations; punishments motivated by prosocial desires may elicit more positive responses than punishments motivated by antisocial desires. We tested both motives that were external to the punisher (the behavior that elicited the punishment) as well as internal motives (the desire to harm versus rehabilitate transgressors). The main result is that we found negative social relationships among punishers, targets, and observers. Both children and adults preferred punishers who inflicted punishment for behaviors that violated (versus did not violate) norms, preferred targets of punishment who had not (versus had) violated norms, and expected punishers and targets to dislike each other. External motives, but not internal motives, consistently influenced participants’ own social preferences. In contrast, neither external nor internal motives consistently shaped participants' inferences about social relationships between punishers and their targets. Our work contributes to social cognitive development by clarifying how motives shape children's and adults' understanding of social relationships. 

Abstract This paper presents experimental studies on a novel active high-frequency coaxial injector system designed for enhanced flow mixing and control at extreme flow velocity conditions. The flow dynamics and mixing characteristics of the system operating at 15kHz were captured using planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV) techniques and compared against its steady and baseline modes. In pulsed mode, this active injection system delivers a pulsed supersonic actuation air jet at the inner core of the coaxial nozzle that provides large mean and fluctuating velocity profiles in the shear layers of an acetone-seeded fluid stream injected surrounding the core through an annular nozzle. The instantaneous velocity, vorticity and acetone concentration fields of the injector are discussed. The high-frequency streamwise vortices and shockwaves tailored to the mean flow significantly enhanced supersonic flow mixing between the fluids compared to a classical steady coaxial configuration operating at the same input pressure. The paper analyses the dynamic and diffusion characteristics of this active coaxial injection system, which may have potential for supersonic mixing applications. 

Punishment can serve as a form of communication: People use punishment to express information to its recipients and interpret punishment between third parties as having communicative content. Prior work on the expressive function of punishment has primarily investigated the capacity of punishment in general to communicate a single type of message – e.g., that the punished behavior violated an important norm. The present work expands this framework by testing whether different types of punishment communicate different messages. We distinguish between person-oriented punishments, which seek to harm the recipient, and action-oriented punishments, which seek to undo a harmful action. We show that people interpret action-oriented punishments, compared to person-oriented punishments, to indicate that the recipient will change for the better (Study 1). The communicative theory can explain this finding if people understand action-oriented punishment to send a message that is more effective than person-oriented punishment at causing such a change. Supporting this explanation, inferences about future behavior track the recipients' beliefs about the punishment they received, rather than the punisher's intentions or the actual punishment imposed (Study 2). Indeed, when actual recipients of a person-oriented punishment believed they received an action-oriented punishment and vice versa, predictions of future behavior tracked the recipients' beliefs rather than reality, and judgments about what the recipients learned from the punishments mediated this effect (Study 3). Together, these studies demonstrate that laypeople think different types of punishment send different messages to recipients and that these messages are differentially effective at bringing about behavioral changes. 

The mixing characteristics of an active coaxial injector in crossflow configurations are explored in this paper. A miniature rectangular CD nozzle generates crossflow for the injector for subsonic and supersonic test conditions. The flowfield of the active injection system consists of an actuation air jet at the inner core of the coaxial nozzle (1mm ID) that provides large mean and fluctuating velocity profiles in the shear layers of a fluid stream injected surrounding the core through an annular nozzle with ID=1.5 mm and OD=1.96 mm. The baseline flowfield of the annular stream in various crossflow conditions was studied first without actuation. The injector's active and passive actuation modes of operation are then evaluated and compared across multiple crossflow conditions with the baseline data. In the active mode, the annular stream is actuated by a pulsed jet operating at 17 kHz. In steady mode, the actuation jet is a steady coaxial underexpanded jet. Measurements using planar laser-induced fluorescence (PLIF) indicate that the active coaxial injection approach using high-frequency pulsed jets at the core significantly improves mixing of the acetone-seeded annular stream in supersonic crossflow conditions compared to the steady and baseline test cases. Data suggests that such a system has the potential to be evaluated further for real-life flow mixing and control applications, such as supersonic and hypersonic combustors. 

The pace and trajectory of ecosystem development are governed by the availability and cycling of limiting nutrients, and anthropogenic disturbances such as acid rain and deforestation alter these trajectories by removing substantial quantities of nutrients via titration or harvest. Here, we use six decades of continuous chemical and hydrologic data from three adjacent headwater catchments in the Hubbard Brook Experimental Forest, New Hampshire—one deforested (W5), one CaSiO₃-enriched (W1), and one reference (W6)—to quantify long-term nutrient and mineral fluxes. Acid deposition since 1900 drove pronounced depletion and export of base cations, particularly calcium, across all watersheds. Experimental deforestation of W5 intensified loss of biomass and nutrient cations and triggered sustained increases in streamwater pH, Ca²⁺, and SiO₂exports over nearly four decades, greatly exceeding the effects of direct CaSiO₃enrichment in both duration and magnitude. We detect no long-term changes in water yield or water flow paths in the experimental watersheds, and we attribute this multidecadal increase in weathering rates following deforestation to biological responses to severe nutrient limitation. Our evidence suggests that in the regrowing forest, plants are investing photosynthate into belowground processes that amplify mineral weathering to access phosphorus and micronutrients, consequently elevating the export of less limiting elements present in silicate parent material. Throughout decades of forest regrowth, enhanced biotic weathering has continued to deplete the acid buffering capacity of the terrestrial ecosystem while the export of weathering products has elevated the pH of the receiving stream. 

We present experiments on chaotic motion of self-propelled (active) particles in a time-independent, two-dimensional vortex chain flow. We track Tetraselmis microbes and calculate the variance of a spreading distribution of these microbes in the flow. For small non-dimensional swimming speed v0, we find subdiffusion with variance ⟨x2⟩∼tγ with γ<1; transport is diffusive (γ=1) for larger v0. Subdiffusion for small v0 is due to dynamic trapping of microbes to islands of ordered trajectories surrounded by a sea of chaotic motion; these islands disappear for larger v0. We calculate Lagrangian-averaged trajectories (LATs) from the experimental data and use the LATs to measure trapping time probability distributions P(t). We find regimes with P(t)∼t−ν with ν<2 for small v0, consistent with the measured subdiffusion.