551 research outputs found
Polarization states of polydomain epitaxial Pb(Zr1-xTix)O3 thin films and their dielectric properties
Ferroelectric and dielectric properties of polydomain (twinned)
single-crystal Pb(Zr1-xTix)O3 thin films are described with the aid of a
nonlinear thermodynamic theory, which has been developed recently for epitaxial
ferroelectric films with dense laminar domain structures. For Pb(Zr1-xTix)O3
(PZT) films with compositions x = 0.9, 0.8, 0.7, 0.6, 0.5, and 0.4, the "misfit
strain-temperature" phase diagrams are calculated and compared with each other.
It is found that the equilibrium diagrams of PZT films with x > 0.7 are similar
to the diagram of PbTiO3 films. They consist of only four different stability
ranges, which correspond to the paraelectric phase, single-domain tetragonal
ferroelectric phase, and two pseudo-tetragonal domain patterns. In contrast, at
x = 0.4, 0.5, and 0.6, the equilibrium diagram displays a rich variety of
stable polarization states, involving at least one monoclinic polydomain state.
Using the developed phase diagrams, the mean out-of-plane polarization of a
poled PZT film is calculated as a function of the misfit strain and
composition. Theoretical results are compared with the measured remanent
polarizations of PZT films grown on SrTiO3. Dependence of the out-of-plane
dielectric response of PZT films on the misfit strain in the heterostructure is
also reported.Comment: 23 pages, 4 figure
Infantsâ preference for social interactions increases from 7 to 13 months of age
This study examined 7-to-13.5-month-old middle-class Western infantsâ visual orienting to third-party interactions in parallel with their social attention behavior during own social interactions (Leipzig, Germany). In Experiment 1, 9.5- to-11-month-olds (n = 20) looked longer than 7- to-8.5-month-olds (n = 20) at videos showing two adults interacting with one another when simultaneously presented with a scene showing two adults acting individually. Moreover, older infants showed higher social engagement (including joint attention) during parentâinfant free play. Experiment 2 replicated this age-related increase in both measures and showed that it follows continuous trajectories from 7 to 13.5 months (n = 50). This suggests that infantsâ attentional orienting to othersâ interactions coincides with parallel developments in their social attention behavior during own social interactions
Expanding the understanding of majority-bias in childrenâs social learning
Prior experiments with children across seven different societies have indicated U-shaped age patterns in the likelihood of copying majority demonstrations. It is unclear which learning strategies underlie the observed responses that create these patterns. Here we broaden the understanding of childrenâs learning strategies by: (1) exploring social learning patterns among 6â13-year-olds (nâ=â270) from ethnolinguistically varied communities in Vanuatu; (2) comparing these data with those reported from other societies (nâ=â629), and (3) re-analysing our and previous data based on a theoretically plausible set of underlying strategies using Bayesian methods. We find higher rates of social learning in children from Vanuatu, a country with high linguistic and cultural diversity. Furthermore, our results provide statistical evidence for modest U-shaped age patterns for a more clearly delineated majority learning strategy across the current and previously investigated societies, suggesting that the developmental mechanisms structuring majority bias are cross-culturally highly recurrent and hence a fundamental feature of early human social learning
Children overâimitate adults and peers more than puppets (advance online)
Researchers commonly use puppets in development science. Amongst other things,puppets are employed to reduce social hierarchies between child participants andadult experimenters akin to peer interactions. However, it remains controversialwhether children treat puppets like real-world social partners in these settings.This study investigated childrenâs imitation of causally irrelevant actions (i.e., over-imitation) performed by puppet, adult, or child models. Seventy-two German children(AgeRange =4.6â6.5 years; 36 girls) from urban, socioeconomically diverse backgroundsobserved a model retrieving stickers from reward containers. The model performedcausally irrelevant actions either in contact with the reward container or not. Childrenwere more likely to over-imitate adultsâ and peersâ actions as compared to puppetsâactions. Across models, they copied contact actions more than no-contact actions.While children imitate causally irrelevant actions from puppet models to some extent,their social learning from puppets does not necessarily match their social learning fromreal-world social agents, such as children or adults
The ontogeny of children's social emotions in response to (un)fairness
Humans have a deeply rooted sense of fairness, but its emotional foundation in early ontogeny remains poorly understood. Here, we asked if and when 4- to 10-year-old children show negative social emotions, such as shame or guilt, in response to advantageous unfairness expressed through a lowered body posture (measured using a Kinect depth sensor imaging camera). We found that older, but not younger children, showed more negative emotions, i.e. a reduced upper body posture, after unintentionally disadvantaging a peer on (4,1) trials than in response to fair (1,1) outcomes between themselves and others. Younger children, in contrast, expressed more negative emotions in response to the fair (1,1) split than in response to advantageous inequity. No systematic pattern of children's emotional responses was found in a non-social context, in which children divided resources between themselves and a non-social container. Supporting individual difference analyses showed that older children in the social context expressed negative emotions in response to advantageous inequity without directly acting on this negative emotional response by rejecting an advantageously unfair offer proposed by an experimenter at the end of the study. These findings shed new light on the emotional foundation of the human sense of fairness and suggest that children's negative emotional response to advantageous unfairness developmentally precedes their rejection of advantageously unfair resource distributions
Small mirrors do the trick: A simple, but effective method to study mirror self-recognition in chimpanzees
Mirror self-recognition (MSR) is considered an indicator of self-awareness. Standardized mirror tests reveal compelling evidence for MSR in a few non-human species, including all great apes. However, substantial inter-individual variation of MSR within species resulted in an ongoing methodological controversy, questioning the appropriateness of standard MSR tests for cross-species comparisons. Lack of motivation, in particular, is discussed as one possible cause for false negative results. Here, we compare the spontaneous behavioral response of 47 zoo-housed chimpanzees (Pan troglodytes) to (i) standard body-sized, stationary mirrors and (ii) small, portable hand mirrors. We predicted that the monopolizability and maneuverability of small mirrors increase the chances of identifying MSR across a larger proportion of individuals. Chimpanzees both revealed a substantially higher frequency of general mirror-related behaviors and engaged in significantly more and longer behaviors specifically indicating MSR when provided with small mirrors compared to a large mirror. Handheld mirrors provide a more sensitive measure for MSR within and likely between primate species than the traditional large mirrors, and thereby are a potentially valuable tool for studying self-awareness across species
A study of the biological effect of continuous inhalation exposure of 1, 1, 1-trichloroethene (methyl chloroform) on animals
The effects of continuous exposure to 1,1,1-trichloroethane on hepatic morphology and function are evaluated and compared with those produced by methylene chloride (dichloromethane) to determine environmental concentrations of each compound that would produce a similar biological response, i.e., a comparable increase in liver triglycerides over control levels. Experimental findings on mice, rats, dogs, and monkeys indicate that the pathological alternations observed with 1,1,1-trichloroethane are similar to those observed with dichloromethane except for different time courses of the effects and different degrees of recovery. A ten fold greater atmospheric concentration of 1,1,1-trichloroethane is required to produce the minimal liver changes found at 100 ppm dichloromethane
Problem solving in the presence of others: How rank and relationship quality impact resource acquisition in chimpanzees (Pan troglodytes)
In the wild, chimpanzees (Pan troglodytes) are often faced with clumped food resources that they may know how to access but abstain from doing so due to social pressures. To better understand how social settings influence resource acquisition, we tested fifteen semi-wild chimpanzees from two social groups alone and in the presence of others. We investigated how resource acquisition was affected by relative social dominance, whether collaborative problem solving or (active or passive) sharing occurred amongst any of the dyads, and whether these outcomes were related to relationship quality as determined from six months of observational data. Results indicated that chimpanzees, regardless of rank, obtained fewer rewards when tested in the presence of others compared to when they were tested alone. Chimpanzees demonstrated behavioral inhibition; chimpanzees who showed proficient skill when alone often abstained from solving the task when in the presence of others. Finally, individuals with close social relationships spent more time together in the problem solving space, but collaboration and sharing were infrequent and sessions in which collaboration or sharing did occur contained more instances of aggression. Group living provides benefits and imposes costs, and these findings highlight that one cost of group living may be diminishing productive individual behaviors
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