A human factors methodology for real-time support applications

A general approach to the human factors (HF) analysis of new or existing projects at NASA/Goddard is delineated. Because the methodology evolved from HF evaluations of the Mission Planning Terminal (MPT) and the Earth Radiation Budget Satellite Mission Operations Room (ERBS MOR), it is directed specifically to the HF analysis of real-time support applications. Major topics included for discussion are the process of establishing a working relationship between the Human Factors Group (HFG) and the project, orientation of HF analysts to the project, human factors analysis and review, and coordination with major cycles of system development. Sub-topics include specific areas for analysis and appropriate HF tools. Management support functions are outlined. References provide a guide to sources of further information

A stellar census of the nearby, young 32 Orionis group

The 32 Orionis group was discovered almost a decade ago and despite the fact that it represents the first northern, young (age ~ 25 Myr) stellar aggregate within 100 pc of the Sun ($d \simeq 93$ pc), a comprehensive survey for members and detailed characterisation of the group has yet to be performed. We present the first large-scale spectroscopic survey for new (predominantly M-type) members of the group after combining kinematic and photometric data to select candidates with Galactic space motion and positions in colour-magnitude space consistent with membership. We identify 30 new members, increasing the number of known 32 Ori group members by a factor of three and bringing the total number of identified members to 46, spanning spectral types B5 to L1. We also identify the lithium depletion boundary (LDB) of the group, i.e. the luminosity at which lithium remains unburnt in a coeval population. We estimate the age of the 32 Ori group independently using both isochronal fitting and LDB analyses and find it is essentially coeval with the {\beta} Pictoris moving group, with an age of $24\pm4$ Myr. Finally, we have also searched for circumstellar disc hosts utilising the AllWISE catalogue. Although we find no evidence for warm, dusty discs, we identify several stars with excess emission in the WISE W4-band at 22 {\mu}m. Based on the limited number of W4 detections we estimate a debris disc fraction of $32^{+12}_{-8}$ per cent for the 32 Ori group.Comment: Accepted for publication in MNRAS; 24 pages, 17 figures and 10 table

Cyanobacteria blooms cannot be controlled by effective microorganisms (EM) from mud- or Bokashi-balls

In controlled experiments, the ability of ‘‘Effective Microorganisms (EM, in the form of mudballs or Bokashi-balls)’’ was tested for clearing waters from cyanobacteria. We found suspensions of EM-mudballs up to 1 g l-1 to be ineffective in reducing cyanobacterial growth. In all controls and EM-mudball treatments up to 1 g l-1 the cyanobacterial chlorophyll-a (Chl-a) concentrations increased within 4 weeks from&120 to 325–435 lg l-1. When pieces of EM-mudballs (42.5 g) were added to 25-l lake water with cyanobacteria, no decrease of cyanobacteria as compared to untreated controls was observed. In contrast, after 4 weeks cyanobacterial Chl-a concentrations were significantly higher in EM-mudball treatments (52 lg l-1) than in controls (20 lg l-1). Only when suspensions with extremely high EM-mudball concentrations were applied (i.e., 5 and 10 g l-1), exceeding the recommended concentrations by orders of magnitude, cyanobacterial growth was inhibited and a bloom forming concentration was reduced strongly. In these high dosing treatments, the oxygen concentration dropped initially to very low levels of 1.8 g l-1. This was most probably through forcing strong light limitation on the cyanobacteria caused by the high amount of clay and subsequent high turbidity of the water. Hence, this study yields no support for the hypothesis that EM is effective in preventing cyanobacterial proliferation or in terminating blooms. We consider EM products to be ineffective because they neither permanently bind nor remove phosphorus from eutroficated systems, they have no inhibiting effect on cyanobacteria, and they could even be an extra source of nutrients

Field Dependent Phase Diagram of the Quantum Spin Chain (CH3)2NH2CuCl3

Although (CH3)2NH2CuCl3 (MCCL) was first examined in the 1930's [1], there are open questions regarding the magnetic dimensionality and nature of the magnetic properties. MCCL is proposed to be a S=1/2 alternating ferromagnetic antiferromagnetic spin chain alternating along the crystalline a-axis [2,3]. Proposed ferromagnetic (JFM =1.3 meV) and antiferromagnetic (JAFM =1.1 meV) exchange constants make this system particularly interesting for experimental study. Because JFM and JAFM are nearly identical, the system should show competing behavior between S=1/2 (AFM) and S=1(FM) effects. We report low temperature magnetic field dependent susceptibility, chi(H), and specific heat, Cp, of MCCL. These provide an initial magnetic-field versus temperature phase diagram. A zero-field phase transition consistent with long range magnetic order is observed at T=0.9 K. The transition temperature can be reduced via application of a magnetic field. We also present comparisons to a FM/AFM dimer model that accounts for chi(T,H=0) and Cp(H,T).Comment: 2 pages, 1 figure included in text. Submitted to proceedings of 24th International Conference on Low Temperature Physics, August 200

A Generalized Theory of Varying Alpha

In this paper, we formulate a generalization of the simple Bekenstein-Sandvik-Barrow-Magueijo (BSBM) theory of varying alpha by allowing the coupling constant, \omega, for the corresponding scalar field \psi\ to depend on \psi. We focus on the situation where \omega\ is exponential in \psi\ and find the late-time behaviours that occur in matter-dominated and dark-energy dominated cosmologies. We also consider the situation when the background expansion scale factor of the universe evolves in proportion to an arbitrary power of the cosmic time. We find the conditions under which the fine structure `constant' increases with time, as in the BSBM theory, and establish a cosmic no-hair behaviour for accelerating universes. We also find the conditions under which the fine structure `constant' can decrease with time and compare the whole family of models with astronomical data from quasar absorption spectra.Comment: 25 pages, 6 figures. Minor corrections and clarifications added. Final section on spatial variations removed so that the paper focuses exclusively on time-variatio

The motion of a satellite of the moon

Analytical solution for motion of lunar orbital satellit

A Chandra Survey of Quasar Jets: First Results

We present results from Chandra X-ray imaging and spectroscopy of a flux-limited sample of flat spectrum radio-emitting quasars with jet-like extended structure. Twelve of twenty quasar jets are detected in 5 ks ACIS-S exposures. The quasars without X-ray jets are not significantly different from those in the sample with detected jets except that the extended radio emission is generally fainter. New radio maps are combined with the X-ray images in order to elucidate the relation between radio and X-ray emission in spatially resolved structures. We find a variety of morphologies, including long straight jets and bends up to 90 degrees. All X-ray jets are one-sided although the radio images used for source selection often show lobes opposite the X-ray jets. The FR II X-ray jets can all be interpreted as inverse Compton scattering of cosmic microwave background photons by electrons in large-scale relativistic jets although deeper observations are required to test this interpretation in detail. Applying this interpretation to the jets as a population, we find that the jets would be aligned to within 30 degrees of the line of sight generally, assuming that the bulk Lorentz factor of the jets is 10.Comment: 25 pages with 5 pages of color figures; accepted for publication in the Astrophysical Journal Supplements; higher resolution jpeg images are available at http://space.mit.edu/home/jonathan/jets

Nonlinear screening and stopping power in two-dimensional electron gases

We have used density functional theory to study the nonlinear screening properties of a two-dimensional (2D) electron gas. In particular, we consider the screening of an external static point charge of magnitude Z as a function of the distance of the charge from the plane of the gas. The self-consistent screening potentials are then used to determine the 2D stopping power in the low velocity limit based on the momentum transfer cross-section. Calculations as a function of Z establish the limits of validity of linear and quadratic response theory calculations, and show that nonlinear screening theory already provides significant corrections in the case of protons. In contrast to the 3D situation, we find that the nonlinearly screened potential supports a bound state even in the high density limit. This behaviour is elucidated with the derivation of a high density screening theorem which proves that the screening charge can be calculated perturbatively in the high density limit for arbitrary dimensions. However, the theorem has particularly interesting implications in 2D where, contrary to expectations, we find that perturbation theory remains valid even when the perturbing potential supports bound states.Comment: 23 pages, 15 figures in RevTeX