F-14 modeling study

Preliminary results in the application of a closed loop pilot/simulator model to the analysis of some simulator fidelity issues are discussed in the context of an air to air target tracking task. The closed loop model is described briefly. Then, problem simplifications that are employed to reduce computational costs are discussed. Finally, model results showing sensitivity of performance to various assumptions concerning the simulator and/or the pilot are presented

General Relativistic Radiative Transfer

We present a general method to calculate radiative transfer including scattering in the continuum as well as in lines in spherically symmetric systems that are influenced by the effects of general relativity (GR). We utilize a comoving wavelength ansatz that allows to resolve spectral lines throughout the atmosphere. The used numerical solution is an operator splitting (OS) technique that uses a characteristic formal solution. The bending of photon paths and the wavelength shifts due to the effects of GR are fully taken into account, as is the treatment of image generation in a curved spacetime. We describe the algorithm we use and demonstrate the effects of GR on the radiative transport of a two level atom line in a neutron star like atmosphere for various combinations of continuous and line scattering coefficients. In addition, we present grey continuum models and discuss the effects of different scattering albedos on the emergent spectra and the determination of effective temperatures and radii of neutron star atmospheres

The development and neural basis of referential gaze perception

Infants are sensitive to the referential information conveyed by others’ eye gaze, which could be one of the developmental foundations of theory of mind. To investigate the neural correlates of gaze–object relations, we recorded ERPs from adults and 9-month-old infants while they watched scenes containing gaze shifts either towards or away from the location of a preceding object. In adults, object-incongruent gaze shifts elicited enhanced ERP amplitudes over the occipito-temporal area (N330). In infants, a similar posterior ERP component (N290) was greater for object-incongruent gaze shifts, which suggests that by the age of 9 months infants encode referential information of gaze in a similar way to adults. In addition, in infants we observed an early frontal ERP component (anterior N200), which showed higher amplitude in response to the perception of object-congruent gaze shifts. This component may reflect fast-track processing of socially relevant information, such as the detection of communicative or informative situations, and could form a developmental foundation for attention sharing, social learning and theory of mind

Non-LTE treatment of molecules in the photospheres of cool stars

We present a technique to treat systems with very many levels, like molecules, in non-LTE. This method is based on a superlevel formalism coupled with rate operator splitting. Superlevels consist of many individual levels that are assumed to be in LTE relative to each other. The usage of superlevels reduces the dimensionality of the rate equations dramatically and, thereby, makes the problem computationally more easily treatable. Our superlevel formalism retains maximum accuracy by using direct opacity sampling (dOS) when calculating the radiative transitions and the opacities. We developed this method in order to treat molecules in cool dwarf model calculations in non-LTE. Cool dwarfs have low electron densities and a radiation field that is far from a black body radiation field, both properties may invalidate the conditions for the common LTE approximation. Therefore, the most important opacity sources, the molecules, need to be treated in non-LTE. As a case study we applied our method to carbon monoxide. We find that our method gives accurate results since the conditions for the superlevel method are very well met for molecules. Due to very high collisional cross sections with hydrogen, and the high densities of H_2 the population of CO itself shows no significant deviation from LTE.Comment: AASTeX v50, 35 pages including 12 figures, accepted by Ap

On the attenuation coefficient of monomode periodic waveguides

It is widely accepted that, on ensemble average, the transmission T of guided modes decays exponentially with the waveguide length L due to small imperfections, leading to the important figure of merit defined as the attenuation-rate coefficient alpha = -/L. In this letter, we evidence that the exponential-damping law is not valid in general for periodic monomode waveguides, especially as the group velocity decreases. This result that contradicts common beliefs and experimental practices aiming at measuring alpha is supported by a theoretical study of light transport in the limit of very small imperfections, and by numerical results obtained for two waveguide geometries that offer contrasted damping behaviours

Atmospheric Analysis of the M/L- and M/T-Dwarf Binary Systems LHS 102 and Gliese 229

We present 0.9-2.5um spectroscopy with R~800 and 1.12-1.22um spectroscopy with R~5800 for the M dwarfs Gl 229A and LHS 102A, and for the L dwarf LHS 102B. We also report IZJHKL' photometry for both components of the LHS 102 system, and L' photometry for Gl 229A. The data are combined with previously published spectroscopy and photometry to produce flux distributions for each component of the kinematically old disk M/L-dwarf binary system LHS 102 and the kinematically young disk M/T-dwarf binary system Gliese 229. The data are analyzed using synthetic spectra generated by the latest "AMES-dusty" and "AMES-cond" models by Allard & Hauschildt. Although the models are not able to reproduce the overall slope of the infrared flux distribution of the L dwarf, most likely due to the treatment of dust in the photosphere, the data for the M dwarfs and the T dwarf are well matched. We find that the Gl 229 system is metal-poor despite having kinematics of the young disk, and that the LHS 102 system has solar metallicity. The observed luminosities and derived temperatures and gravities are consistent with evolutionary model predictions if the Gl 229 system is very young (age ~30 Myr) with masses (A,B) of (0.38,>0.007)M(sun), and the LHS 102 system is older, aged 1-10 Gyr with masses (A,B) of (0.19,0.07)M(sun).Comment: 29 pages incl. 13 figures and 5 tables;; accepted for publication in MNRA