The I in Autism:severity and social functioning in Autism is related to self-processing

It is well established that children with autism spectrum disorder (ASD) show impaired understanding of others and deficits within social functioning. However, it is still unknown whether self-processing is related to these impairments and to what extent self impacts social functioning and communication. Using an ownership paradigm, we show that children with ASD and chronological- and verbal-age-matched typically developing (TD) children do show the self-referential effect in memory. In addition, the self-bias was dependent on symptom severity and socio-communicative ability. Children with milder ASD symptoms were more likely to have a high self-bias, consistent with a low attention to others relative to self. In contrast, severe ASD symptoms were associated with reduced self-bias, consistent with an ‘absent-self’ hypothesis. These findings indicate that deficits in self-processing may be related to impairments in social cognition for those on the lower end of the autism spectrum

The effect of applied magnetic field on photocurrent generation in poly-3-hexylthiophene:[6,6]-phenyl C61-butyric acid methyl ester photovoltaic devices

This is the author’s version of a work that was accepted for publication in Journal of Physics: Condensed Matter http://dx.doi.org/10.1088/0953-8984/20/45/45220

Apparent Seasonal Cycle in Isotopic Discrimination of Carbon in the Atmosphere and Biosphere Due to Vapor Pressure Deficit

We explore seasonal variability in isotopic fractionation by analyzing observational data from the atmosphere and the biosphere, as well as simulated data from a global model. Using simulated values of atmospheric CO2 and its carbon isotopic composition, we evaluated different methods for specifying background concentrations when calculating the isotopic signature of source CO2 (δs) to the atmosphere. Based on this evaluation, we determined that free troposphere measurements should be used when available as a background reference when calculating δs from boundary layer observations. We then estimate the seasonal distribution of δs from monthly climatologies derived from several atmospheric sampling sites. This approach yields significant seasonal variations in δs with more enriched values during the summer months that exceed the uncertainty of δs estimated for any given month. Intra-annual measurements of δ13C in the cellulose of Pinus taeda growing in the southeastern U.S. also reveal seasonal isotopic variations that are consistent in phase but not necessarily amplitude with atmospherically derived estimates of δs. Coherent seasonal patterns in δs inferred from the atmosphere and observed in the biosphere were not consistent with the seasonal isotopic discrimination simulated by a commonly used biosphere model. However, δs seasonality consistent with observations from the atmosphere and biosphere was retrieved with a revised biosphere model when stomatal conductance, and thus isotopic discrimination, was allowed to vary in response to vapor pressure deficit rather than relative humidity. Therefore, in regions where vapor pressure deficit and relative humidity are positively covariant over the growth season, such as the sub-tropics, different stomatal conductance models may yield very different estimates of CO2 and H2O exchange between the biosphere and atmosphere

Impact of neutron star spin on Poynting-Robertson drag during a Type I X-ray burst

External irradiation of a neutron star (NS) accretion disc induces Poynting-Robertson (PR) drag, removing angular momentum and increasing the mass accretion rate. Recent simulations show PR drag significantly enhancing the mass accretion rate during Type I X-ray bursts, which could explain X-ray spectral features such as an increase in the persistent emission and a soft excess. However, prograde spin of the NS is expected to weaken PR drag, challenging its importance during bursts. Here, we study the effect of spin on PR drag during X-ray bursts. We run four simulations, with two assuming a non-spinning NS and two using a spin parameter of $a_*=0.2$, corresponding to a rotation frequency of 500 Hz. For each scenario, we simulate the disc evolution subject to an X-ray burst and compare it to the evolution found with no burst. PR drag drains the inner disc region during a burst, moving the inner disc radius outward by $\approx1.6$ km in the $a_*=0$ and by $\approx2.2$ km in the $a_*=0.2$ simulation. The burst enhances the mass accretion rate across the innermost stable circular orbit $\approx7.9$ times when the NS is not spinning and $\approx11.2$ times when it is spinning. The explanation for this seemingly contradictory result is that the disc is closer to the NS when $a_*=0.2$, and the resulting stronger irradiating flux offsets the weakening effect of spin on the PR drag. Hence, PR drag remains a viable explanation for the increased persistent emission and soft excess observed during X-ray bursts in spinning NS systems.Comment: 9 pages, 8 figures, accepted for publication in MNRA

Regional Differences in South American Monsoon Precipitation Inferred from the Growth and Isotopic Composition of Tropical Trees

The authors present results on the relationship between tree-ring proxies and regional precipitation for several sites in tropical South America. The responsiveness of oxygen isotopes (δ18O) and seasonal growth as precipitation proxies was first validated by high-resolution sampling of a Tachigali myrmecophila from Manaus, Brazil (3.1°S, 60.0°W). Monthly growth of Tachigali spp. was significantly correlated with monthly precipitation. Intra-annual measurements of cellulose δ18O in Tachigali spp. were also significantly correlated with monthly precipitation at a lag of approximately one month. The annual ring widths of two tropical tree taxa, Cedrela odorata growing in the Amazon (12.6°S, 69.2°W) and Polylepis tarapacana growing in the Altiplano (22.0°S, 66.0°W), were validated using bomb-derived radiocarbon 14C. Estimated dates were within two to three years of bomb-inferred 14C dates, indicating that these species exhibit annual rings but uncertainties in our chronologies remain. A multiproxy record spanning 180 years from Cedrela spp. showed a significant negative relationship between cellulose δ18O and January precipitation. A 150-yr record obtained from Polylepis spp. also showed a significant negative relationship between δ18O and March precipitation, whereas annual ring width showed a significant positive correlation with December precipitation. These proxies were combined in a multivariate framework to reconstruct past precipitation, revealing a significant increase in monsoon precipitation at the Amazon site since 1890 and a significant decrease in monsoon precipitation at the Altiplano since 1880. Proxy time series also showed spatial and temporal coherence with precipitation variability due to El Niño forcing, suggesting that oxygen isotopes and ring widths in tropical trees may be important diagnostics for identifying regional differences in the response of the tropical hydrologic cycle to anthropogenic warming

The Primordial Helium Abundance: Toward Understanding and Removing the Cosmic Scatter in the \u3cem\u3eDY/DZ\u3c/em\u3e Relation

We present results from photoionization models of low-metallicity H II regions. These nebulae form the basis for measuring the primordial helium abundance. Our models show that the helium ionization correction factor (ICF) can be nonnegligible for nebulae excited by stars with effective temperatures larger than 40,000 K. Furthermore, we find that when the effective temperature rises to above 45,000 K, the ICF can be significantly negative. This result is independent of the choice of stellar atmosphere. However, if an H II region has an [O III] λ5007/[O I] λ6300 ratio greater than 300, then our models show that, regardless of its metallicity, it will have a negligibly small ICF. A similar, but metallicity-dependent, result was found using the [O III] λ5007/Hβ ratio. These two results can be used as selection criteria to remove nebulae with potentially nonnegligible ICFs. Use of our metallicity-independent criterion on the data of Izotov & Thuan results in a 20% reduction of the rms scatter about the best-fit Y-Z line. A fit to the selected data results in a slight increase of the value of the primordial helium abundance

Probing X-ray burst -- accretion disk interaction in low mass X-ray binaries through kilohertz quasiperiodic oscillations

The intense radiation flux of Type I X-ray bursts is expected to interact with the accretion flow around neutron stars. High frequency quasiperiodic oscillations (kHz QPOs), observed at frequencies matching orbital frequencies at tens of gravitational radii, offer a unique probe of the innermost disk regions. In this paper, we follow the lower kHz QPOs, in response to Type I X-ray bursts, in two prototypical QPO sources, namely 4U 1636-536 and 4U 1608-522, as observed by the Proportional Counter Array of the Rossi X-ray Timing Explorer. We have selected a sample of 15 bursts for which the kHz QPO frequency can be tracked on timescales commensurable with the burst durations (tens of seconds). We find evidence that the QPOs are affected for over ~200 s during one exceptionally long burst and ~100 s during two others (although at a less significant level), while the burst emission has already decayed to a level that would enable the pre-burst QPO to be detected. On the other hand, for most of our burst-kHz QPO sample, we show that the QPO is detected as soon as the statistics allow and in the best cases, we are able to set an upper limit of ~20 s on the recovery time of the QPO. This diversity of behavior cannot be related to differences in burst peak luminosity. We discuss these results in the framework of recent findings that accretion onto the neutron star may be enhanced during Type I X-ray bursts. The subsequent disk depletion could explain the disappearance of the QPO for ~100 s, as possibly observed in two events. However, alternative scenarios would have to be invoked for explaining the short recovery timescales inferred from most bursts. Clearly the combination of fast timing and spectral information of Type I X-ray bursts holds great potential in the study of the dynamics of the inner accretion flow around neutron stars.Comment: 8 pages, 9 figures, appears in Astronomy & Astrophysics, Volume 567, id.A80, published 07/201

Connecting Galaxy Evolution, Star Formation and the X-ray Background

As a result of deep hard X-ray observations by Chandra and XMM-Newton a significant fraction of the cosmic X-ray background (CXRB) has been resolved into individual sources. These objects are almost all active galactic nuclei (AGN) and optical followup observations find that they are mostly obscured Type 2 AGN, have Seyfert-like X-ray luminosities (i.e., L_X ~ 10^{43-44} ergs s^{-1}), and peak in redshift at z~0.7. Since this redshift is similar to the peak in the cosmic star-formation rate, this paper proposes that the obscuring material required for AGN unification is regulated by star-formation within the host galaxy. We test this idea by computing CXRB synthesis models with a ratio of Type 2/Type 1 AGN that is a function of both z and 2-10 keV X-ray luminosity, L_X. The evolutionary models are constrained by parameterizing the observed Type 1 AGN fractions from the recent work by Barger et al. The parameterization which simultaneously best accounts for Barger's data, the CXRB spectrum and the X-ray number counts has a local, low-L_X Type 2/Type 1 ratio of 4, and predicts a Type 2 AGN fraction which evolves as (1+z)^{0.3}. Models with no redshift evolution yielded much poorer fits to the Barger Type 1 AGN fractions. This particular evolution predicts a Type 2/Type 1 ratio of 1-2 for log L_X > 44, and thus the deep X-ray surveys are missing about half the obscured AGN with these luminosities. These objects are likely to be Compton thick. Overall, these calculations show that the current data strongly supports a change to the AGN unification scenario where the obscuration is connected with star formation in the host galaxy rather than a molecular torus alone. The evolution of the obscuration implies a close relationship between star formation and AGN fueling, most likely due to minor mergers or interactions.Comment: 36 pages, 8 figures, ApJ in press. Minor changes to match published versio

Novel Applications of Carbon Isotopes in Atmospheric CO2: What Can Atmospheric Measurements Teach Us About Processes in the Biosphere?

Conventionally, measurements of carbon isotopes in atmospheric CO2 (δ13CO2) have been used to partition fluxes between terrestrial and ocean carbon pools. However, novel analytical approaches combined with an increase in the spatial extent and frequency of δ13CO2 measurements allow us to conduct a global analysis of δ13CO2 variability to infer the isotopic composition of source CO2 to the atmosphere (δs). This global analysis yields coherent seasonal patterns of isotopic enrichment. Our results indicate that seasonal values of δs are more highly correlated with vapor pressure deficit (r = 0.404) than relative humidity (r = 0.149). We then evaluate two widely used stomatal conductance models and determine that the Leuning Model, which is primarily driven by vapor pressure deficit is more effective globally at predicting δs (RMSE = 1.6‰) than the Ball-Woodrow-Berry model, which is driven by relative humidity (RMSE = 2.7‰). Thus stomatal conductance on a global scale may be more sensitive to changes in vapor pressure deficit than relative humidity. This approach highlights a new application of using δ13CO2 measurements to validate global models