Transformations and representations supporting spatial perspective taking

Spatial perspective taking is the ability to reason about spatial relations relative to another’s viewpoint. Here, we propose a mechanistic hypothesis that relates mental representations of one’s viewpoint to the transformations used for spatial perspective taking. We test this hypothesis using a novel behavioral paradigm that assays patterns of response time and variation in those patterns across people. The results support the hypothesis that people maintain a schematic representation of the space around their body, update that representation to take another’s perspective, and thereby to reason about the space around their body. This is a powerful computational mechanism that can support imitation, coordination of behavior, and observational learning.     

Using altimetry and seafloor pressure data to estimate vertical deformation offshore: Vanuatu case study

Measuring ground deformation underwater is essential for understanding Earth processes at many scales. One important example is subduction zones, which can generate devastating earthquakes and tsunamis, and where the most important deformation signal related to plate locking is usually offshore. We present an improved method for making offshore vertical deformation measurements, that involve combining tide gauge and altimetry data. We present data from two offshore sites located on either side of the plate interface at the New Hebrides subduction zone, where the Australian plate subducts beneath the North Fiji basin. These two sites have been equipped with pressure gauges since 1999, to extend an on-land GPS network across the plate interface. The pressure series measured at both sites show that Wusi Bank, located on the over-riding plate, subsides by 11 ± 4 mm/yr with respect to Sabine Bank, which is located on the down-going plate. By combining water depths derived from the on-bottom pressure data with sea surface heights derived from altimetry data, we determine variations of seafloor heights in a global reference frame. Using altimetry data from TOPEX/Poseidon, Jason-1, Jason-2 and Envisat missions, we find that the vertical motion at Sabine Bank is close to zero and that Wusi Bank subsides by at least 3 mm/yr and probably at most 11 mm/yr.     

S5 0716+714: GeV variability study

The GeV observations by Fermi-LAT give us the opportunity to characterize the high-energy emission (100 MeV–300 GeV) variability properties of the BL Lac object S5 0716+714. In this study, we performed flux and spectral analysis of more than 3 year long (August 2008 to April 2012) Fermi-LAT data of the source. During this period, the source exhibits two different modes of flux variability with characteristic timescales of ∼75 and ∼140 days, respectively. We also notice that the flux variations are characterized by a weak spectral hardening. The GeV spectrum of the source shows a clear deviation from a simple power law, and is better explained by a broken power law. Similar to other bright Fermi blazars, the break energy does not vary with the source flux during the different activity states. We discuss several possible scenarios to explain the observed spectral break.     

Below One Earth: The Detection, Formation, and Properties of Subterrestrial Worlds

The Solar System includes two planets—Mercury and Mars—significantly less massive than Earth, and all evidence indicates that planets of similar size orbit many stars. In fact, one of the first exoplanets to be discovered is a lunar-mass planet around a millisecond pulsar. Novel classes of exoplanets have inspired new ideas about planet formation and evolution, and these “sub-Earths” should be no exception: they include planets with masses between Mars and Venus for which there are no Solar System analogs. Advances in astronomical instrumentation and recent space missions have opened the sub-Earth frontier for exploration: the Kepler mission has discovered dozens of confirmed or candidate sub-Earths transiting their host stars. It can detect Mars-size planets around its smallest stellar targets, as well as exomoons of comparable size. Although the application of the Doppler method is currently limited by instrument stability, future spectrographs may detect equivalent planets orbiting close to nearby bright stars. Future space-based microlensing missions should be able to probe the sub-Earth population on much wider orbits. A census of sub-Earths will complete the reconnaissance of the exoplanet mass spectrum and test predictions of planet formation models, including whether low-mass M dwarf stars preferentially host the smallest planets. The properties of sub-Earths may reflect their low gravity, diverse origins, and environment, but they will be elusive: Observations of eclipsing systems by the James Webb Space Telescope may give us our first clues to the properties of these small worlds.     

On the nature of coronal loops above the quiet sun network

The structure and dynamics of a box in a stellar corona can be modeled employing a 3D MHD model for different levels of magnetic activity. Depending on the magnetic flux through the surface the nature of the resulting coronal structures can be quite different. We investigate a model of an active region for two sunspots surrounded by magnetic field patches comparable in magnetic flux to the sunspots. The model results in emission from the model corona being concentrated in loop structures. In Gudiksen and Nordlund (2005) the loops seen in EUV and X-ray emission outline the magnetic field, following the general paradigm. However, in our model, where the magnetic field is far from a force-free state, the loops seen in X-ray emission do not follow the magnetic field lines. This result is of interest especially for loops as found in areas where the magnetic field emerging from active regions interacts with the surrounding network.     

Cosmic ray hits in the central nervous system at solar maximum.

It has been suggested that a manned mission to Mars be launched at solar maximum rather than at solar minimum to minimize the radiation exposure to galactic cosmic rays. It is true that the number of hits from highly ionizing particles to critical regions in the brain will be less at solar maximum, and it is of interest to estimate how much less. We present here calculations for several sites within the brain from iron ions (z = 26) and from particles with charge, z, greater than or equal to 15. The same shielding configurations and sites in the brain used in an earlier paper for solar minimum are employed so that direct comparison of results between the two solar activity conditions can be made. A simple pressure-vessel wall and an equipment room onboard a spacecraft are chosen as shielding examples. In the equipment room, typical results for the thalamus are that the probability of any particles with 7 greater than or equal to 15 and from 2.3 percent to 1.3 percent for iron ions. The extra shielding provided in the equipment room makes little difference in these numbers. We conclude that this decrease in hit frequency (less than a factor of two) does not provide a compelling reason to avoid solar minimum for a manned mission to Mars. This conclusion could be revised, however, if a very small number of hits is found to cause critical malfunction within the brain.     

Thermodynamic properties of gases at combustion of heavy distillate fuels

Based on the data on composition and calorific power of diesel fuel and solar oil, the conditional expressions of fuels and values of their enthalpies are considered. The data on thermodynamic properties of combustion products are obtained and generalized by calculating the process of air-fuel mixture combustion in a wide range of parameter variations.     

Stabilization of an injected conducting layer for artificially enhancing drag on orbital debris

The evolution of a magnetized conducting medium suspended in magnetic and gravitational fields is examined. In this paper some effects of the influence of velocity fields on the linear stability properties of such layers are investigated. A fully compressible, three-dimensional analysis of the layer is described. The relevant equations are derived and then solved by the MagnetoHydroDynamic SPEctral Compressible Linear Stability (MHDSPECLS) algorithm, a Chebyshev collocation code. The code allows for the computation of magnetic and thermal effects. A complete stabilization of the system is found above a critical velocity of approximately 2500 m/s.     

Study of the mesosphere using wide-field twilight polarization measurements: Early results beyond the polar circle

This paper discusses the results of early measurements of temperature and dust in the mesosphere on the basis of wide-field twilight sky polarimetry, which began in 2015 in Apatity (North of Russia, 67.6° N, 33.4° E) using the original entire-sky camera. These measurements have been performed for the first time beyond the Polar Circle in the winter and early spring period. The general polarization properties of the twilight sky and the procedure for identifying single scattering are described. The key results of the study include the Boltzmann temperature values at altitudes higher than 70 km and the conclusion on a weak effect of dust on scattering properties of the mesosphere during this period.