Social re-orientation and brain development: An expanded and updated view.

Social development has been the focus of a great deal of neuroscience based research over the past decade. In this review, we focus on providing a framework for understanding how changes in facets of social development may correspond with changes in brain function. We argue that (1) distinct phases of social behavior emerge based on whether the organizing social force is the mother, peer play, peer integration, or romantic intimacy; (2) each phase is marked by a high degree of affect-driven motivation that elicits a distinct response in subcortical structures; (3) activity generated by these structures interacts with circuits in prefrontal cortex that guide executive functions, and occipital and temporal lobe circuits, which generate specific sensory and perceptual social representations. We propose that the direction, magnitude and duration of interaction among these affective, executive, and perceptual systems may relate to distinct sensitive periods across development that contribute to establishing long-term patterns of brain function and behavior

Magellan/MMIRS near-infrared multi-object spectroscopy of nebular emission from star forming galaxies at 2<z<3

To investigate the ingredients, which allow star-forming galaxies to present Lyalpha line in emission, we studied the kinematics and gas phase metallicity (Z) of the interstellar medium. We used multi-object NIR spectroscopy with Magellan/MMIRS to study nebular emission from z=2-3 star-forming galaxies discovered in 3 MUSYC fields. We detected emission lines from four active galactic nuclei and 13 high-z star-forming galaxies, including Halpha lines down to a flux of 4.E-17 erg/sec/cm^2. This yielded 7 new redshifts. The most common emission line detected is [OIII]5007, which is sensitive to Z. We were able to measure Z for 2 galaxies and to set upper(lower) limits for another 2(2). The Z values are consistent with 0.3<Z/Zsun<1.2. Comparing the Lyalpha central wavelength with the systemic redshift, we find Delta_v(Lyalpha-[OIII])=70-270 km/sec. High-redshift star-forming galaxies, Lyalpha emitting (LAE) galaxies, and Halpha emitters appear to be located in the low mass, high star-formation rate (SFR) region of the SFR versus stellar mass diagram, confirming that they are experiencing burst episodes of star formation, which are building up their stellar mass. Their Zs are consistent with the relation found for z<2.2 galaxies in the Z versus stellar mass plane. The measured Delta_v(Lyalpha-[OIII]) values imply that outflows of material, driven by star formation, could be present in the z=2-3 LAEs of our sample. Comparing with the literature, we note that galaxies with lower Z than ours are also characterized by similar Delta_v(Lyalpha-[OIII]) velocity offsets. Strong [OIII] is detected in many Lyalpha emitters. Therefore, we propose the Lyalpha/[OIII] flux ratio as a tool for the study of high-z galaxies; while influenced by Z, ionization, and Lyalpha radiative transfer in the ISM, it may be possible to calibrate this ratio to primarily trace one of these effects.Comment: 22 pages, 13 figures, 6 table

An Empirically Derived Three-Dimensional Laplace Resonance in the Gliese 876 Planetary System

We report constraints on the three-dimensional orbital architecture for all four planets known to orbit the nearby M dwarf Gliese 876 based solely on Doppler measurements and demanding long-term orbital stability. Our dataset incorporates publicly available radial velocities taken with the ELODIE and CORALIE spectrographs, HARPS, and Keck HIRES as well as previously unpublished HIRES velocities. We first quantitatively assess the validity of the planets thought to orbit GJ 876 by computing the Bayes factors for a variety of different coplanar models using an importance sampling algorithm. We find that a four-planet model is preferred over a three-planet model. Next, we apply a Newtonian MCMC algorithm to perform a Bayesian analysis of the planet masses and orbits using an n-body model in three-dimensional space. Based on the radial velocities alone, we find that a 99% credible interval provides upper limits on the mutual inclinations for the three resonant planets ($\Phi_{cb}<6.20^\circ$ for the "c" and "b" pair and $\Phi_{be}<28.5^\circ$ for the "b" and "e" pair). Subsequent dynamical integrations of our posterior sample find that the GJ 876 planets must be roughly coplanar ($\Phi_{cb}<2.60^\circ$ and $\Phi_{be}<7.87^\circ$), suggesting the amount of planet-planet scattering in the system has been low. We investigate the distribution of the respective resonant arguments of each planet pair and find that at least one argument for each planet pair and the Laplace argument librate. The libration amplitudes in our three-dimensional orbital model supports the idea of the outer-three planets having undergone significant past disk migration.Comment: 19 pages, 11 figures, 8 tables. Accepted to MNRAS. Posterior samples available at https://github.com/benelson/GJ87

The 55 Cancri Planetary System: Fully Self-Consistent N-body Constraints and a Dynamical Analysis

We present an updated study of the planets known to orbit 55 Cancri A using 1,418 high-precision radial velocity observations from four observatories (Lick, Keck, Hobby-Eberly Telescope, Harlan J. Smith Telescope) and transit time/durations for the inner-most planet, 55 Cancri "e" (Winn et al. 2011). We provide the first posterior sample for the masses and orbital parameters based on self-consistent n-body orbital solutions for the 55 Cancri planets, all of which are dynamically stable (for at least $10^8$ years). We apply a GPU version of Radial velocity Using N-body Differential evolution Markov Chain Monte Carlo (RUN DMC; B. Nelson et al. 2014) to perform a Bayesian analysis of the radial velocity and transit observations. Each of the planets in this remarkable system has unique characteristics. Our investigation of high-cadence radial velocities and priors based on space-based photometry yields an updated mass estimate for planet "e" ($8.09\pm0.26$ M$_\oplus$), which affects its density ($5.51\pm^{1.32}_{1.00}$ g cm$^{-3}$) and inferred bulk composition. Dynamical stability dictates that the orbital plane of planet "e" must be aligned to within $60^o$ of the orbital plane of the outer planets (which we assume to be coplanar). The mutual interactions between the planets "b" and "c" may develop an apsidal lock about $180^o$. We find 36-45% of all our model systems librate about the anti-aligned configuration with an amplitude of $51^o\pm^{6^o}_{10^o}$. Other cases showed short-term perturbations in the libration of $\varpi_b-\varpi_c$, circulation, and nodding, but we find the planets are not in a 3:1 mean-motion resonance. A revised orbital period and eccentricity for planet "d" pushes it further toward the closest known Jupiter analog in the exoplanet population.Comment: 12 pages, 5 figures, 4 tables, accepted to MNRAS. Figure 2 (left) is updated from published version. Posterior samples available at http://www.personal.psu.edu/ben125/Downloads.htm

Probing the Neural Correlates of Anticipated Peer Evaluation in Adolescence

Neural correlates of social cognition were assessed in 9-to-17-year-olds using functional magnetic resonance imaging (fMRI). Participants appraised how unfamiliar peers they had previously identified as being of high or low interest would evaluate them for an anticipated online chat session. Differential age- and sex-related activation patterns emerged in several regions previously implicated in affective processing. These included the ventral striatum, hippocampus, hypothalamus, and insula. In general, activation patterns shifted with age in older relative to younger females, but showed no association with age in males. Relating these neural response patterns to changes in adolescent social-cognition enriches theories of adolescent social development through enhanced neurobiological understanding of social behavior

Associations Between Adolescents’ Social Re-orientation Toward Peers Over Caregivers and Neural Response to Teenage Faces

Adolescence is a period of intensive development in body, brain, and behavior. Potentiated by changes in hormones and neural response to social stimuli, teenagers undergo a process of social re-orientation away from their caregivers and toward expanding peer networks. The current study examines how relative relational closeness to peers (compared to parents) during adolescence is linked to neural response to the facial emotional expressions of other teenagers. Self-reported closeness with friends (same- and opposite-sex) and parents (mother and father), and neural response to facial stimuli during fMRI, were assessed in 8- to 19-year-old typically developing youth (n = 40, mean age = 13.90 years old, SD = 3.36; 25 female). Youth who reported greater relative closeness with peers than with parents showed decreased activation in the dorsolateral prefrontal cortex (dlPFC) during stimulus presentation, which may reflect lessened inhibitory control or regulatory response to peer-aged faces. Functional connectivity between the dlPFC and dorsal striatum was greatest in older youth who were closer to peers; in contrast, negative coupling between these regions was noted for both younger participants who were closer to peers and older participants who were closer to their parents. In addition, the association between relative closeness to peers and neural activation in regions of the social brain varied by emotion type and age. Results suggest that the re-orientation toward peers that occurs during adolescence is accompanied by changes in neural response to peer-aged social signals in social cognitive, prefrontal, and subcortical networks

Do ultrafast exciton-polaron decoherence dynamics govern photocarrier generation efficiencies in polymer solar cells?

All-organic-based photovoltaic solar cells have attracted considerable attention because of their low-cost processing and short energy payback time. In such systems the primary dissociation of an optical excitation into a pair of photocarriers has been recently shown to be extremely rapid and efficient, but the physical reason for this remains unclear. Here, two-dimensional photocurrent excitation spectroscopy, a novel non-linear optical spectroscopy, is used to probe the ultrafast coherent decay of photoexcitations into charge-producing states in a polymer:fullerene based solar cell. The two-dimensional photocurrent spectra are interpreted by introducing a theoretical model for the description of the coupling of the electronic states of the system to an external environment and to the applied laser fields. The experimental data show no cross-peaks in the two-dimensional photocurrent spectra, as predicted by the model for coherence times between the exciton and the photocurrent producing states of 20\,fs or less