The cluster of galaxies Abell 2199.
Abell 2199 cluster of galaxies, discussing population contours, volume density function, structure and other static properties
Clark, E. E.↗
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Interstellar carbon I lines in zeta Ophiuchi
With two f-values of C I lines obtained from the spectra of zeta Pup and gamma(2) Vel, it is shown that the interstellar C I spectrum in zeta Oph obeys an optical-depth relation similar to that for Na I, and the relative strengths of 19 multiplets are determined from this relation. The dominant processes which excite neutral carbon are used to calculate populations of the fine-structure levels as functions of the density of H nuclei and the temperature, and evidence is found that the C I lines are formed in the dense cloud in front of zeta Oph at a heliocentric velocity of -14.4 km/s. It is noted that the observed column-density ratios of the neutral carbon fine-structure levels lead to a total H nuclei density of about 220 to 660 per cu cm, while the electron density and observed C(+) abundance indicate a value of 10,000 per cu cm, with a 0.05 pc thick gas layer.
De Boer, K. S.↗
Interstellar absorption lines in the spectrum of zeta Ophiuchi
Extensive high-resolution scans with the Copernicus UV spectrometer are combined with available ground-based data on interstellar lines to obtain temperatures, densities, and abundances in H I clouds and H II regions in the direction of zeta Oph. Column densities are obtained for 21 elements in various ionization stages, and upper limits are reported for 5 elements and 11 molecules. Analysis of radial velocities and growth curves indicates that H2, HD, and most neutral atoms are concentrated in one cloud with a heliocentric velocity of -14.4 km/s and that H II regions exist in addition to the Stroemgren sphere. The electron and proton densities are calculated for the -14.4 km/s cloud, and the temperatures required for the populations of the fine-structure levels in the C I ground state and the excited rotational levels of H2 are computed and indicate that the dense cloud must have some associated hotter regions. Relative to hydrogen, most of the elements in the H I clouds are found to be depleted by factors of 3 to 4000 as compared with solar system abundances, and several elements appear to be depleted in the H II regions as well.
Morton, D. C.↗
Catastrophic disruption in the solar system - Asteroid collisional history, origin of Hirayama families and disruption of small satellites
The process of collisional catastrophic disruption has played a significantly role in structuring the solar system. Diverse populations of bodies such as the asteroid belt, small satellites of Jupiter and Saturn and perhaps even the rings of Saturn have been created or substantially changed by catastrophic distruption. Understanding the outcome of large scale impacts is essential to learning about the early history of the solar system in the asteroid zone and the reason why a planet failed to form there.
Davis, D. R.↗
Optical signatures of high-redshift galaxy clusters
We combine an N-body and gasdynamic simulation of structure formation with an updated population synthesis code to explore the expected optical characteristics of a high-redshift cluster of galaxies. We examine a poor (2 keV) cluster formed in a biased, cold dark matter cosmology and employ simple, but plausible, threshold criteria to convert gas into stars. At z = 2, the forming cluster appears as a linear chain of very blue (g-r approximately equals 0) galaxies, with 15 objects brighter than r = 25 within a 1 square arcmin field of view. After 2 Gyr of evolution, the cluster viewed at z = 1 displays both freshly infalling blue galaxies and red galaxies robbed of recent accretion by interaction with the hot intracluster medium. The range in G-R colors is approximately 3 mag at z = 1, with the reddest objects lying at sites of highest galaxy density. We suggest that red, high-redshift galaxies lie in the cores of forming clusters and that their existence indicates the presence of a hot intracluster medium at redshifts z approximately equals 2. The simulated cluster viewed at z = 2 has several characteristics similar to the collection of faint, blue objects identified by Dressler et al. in a deep Hubble Space Telescope observation. The similarities provide some support for the interpretation of this collection as a high-redshift cluster of galaxies.
Evrard, August E.↗
On the nature and evolution of the neural bases of human language
The traditional theory equating the brain bases of language with Broca's and Wernicke's neocortical areas is wrong. Neural circuits linking activity in anatomically segregated populations of neurons in subcortical structures and the neocortex throughout the human brain regulate complex behaviors such as walking, talking, and comprehending the meaning of sentences. When we hear or read a word, neural structures involved in the perception or real-world associations of the word are activated as well as posterior cortical regions adjacent to Wernicke's area. Many areas of the neocortex and subcortical structures support the cortical-striatal-cortical circuits that confer complex syntactic ability, speech production, and a large vocabulary. However, many of these structures also form part of the neural circuits regulating other aspects of behavior. For example, the basal ganglia, which regulate motor control, are also crucial elements in the circuits that confer human linguistic ability and abstract reasoning. The cerebellum, traditionally associated with motor control, is active in motor learning. The basal ganglia are also key elements in reward-based learning. Data from studies of Broca's aphasia, Parkinson's disease, hypoxia, focal brain damage, and a genetically transmitted brain anomaly (the putative "language gene," family KE), and from comparative studies of the brains and behavior of other species, demonstrate that the basal ganglia sequence the discrete elements that constitute a complete motor act, syntactic process, or thought process. Imaging studies of intact human subjects and electrophysiologic and tracer studies of the brains and behavior of other species confirm these findings. As Dobzansky put it, "Nothing in biology makes sense except in the light of evolution" (cited in Mayr, 1982). That applies with as much force to the human brain and the neural bases of language as it does to the human foot or jaw. The converse follows: the mark of evolution on the brains of human beings and other species provides insight into the evolution of the brain bases of human language. The neural substrate that regulated motor control in the common ancestor of apes and humans most likely was modified to enhance cognitive and linguistic ability. Speech communication played a central role in this process. However, the process that ultimately resulted in the human brain may have started when our earliest hominid ancestors began to walk.
Review, Tutorial↗
Adaptable Constrained Genetic Programming: Extensions and Applications
An evolutionary algorithm applies evolution-based principles to problem solving. To solve a problem, the user defines the space of potential solutions, the representation space. Sample solutions are encoded in a chromosome-like structure. The algorithm maintains a population of such samples, which undergo simulated evolution by means of mutation, crossover, and survival of the fittest principles. Genetic Programming (GP) uses tree-like chromosomes, providing very rich representation suitable for many problems of interest. GP has been successfully applied to a number of practical problems such as learning Boolean functions and designing hardware circuits. To apply GP to a problem, the user needs to define the actual representation space, by defining the atomic functions and terminals labeling the actual trees. The sufficiency principle requires that the label set be sufficient to build the desired solution trees. The closure principle allows the labels to mix in any arity-consistent manner. To satisfy both principles, the user is often forced to provide a large label set, with ad hoc interpretations or penalties to deal with undesired local contexts. This unfortunately enlarges the actual representation space, and thus usually slows down the search. In the past few years, three different methodologies have been proposed to allow the user to alleviate the closure principle by providing means to define, and to process, constraints on mixing the labels in the trees. Last summer we proposed a new methodology to further alleviate the problem by discovering local heuristics for building quality solution trees. A pilot system was implemented last summer and tested throughout the year. This summer we have implemented a new revision, and produced a User's Manual so that the pilot system can be made available to other practitioners and researchers. We have also designed, and partly implemented, a larger system capable of dealing with much more powerful heuristics.
Janikow, Cezary Z.↗
NASA's New Orbital Debris Engineering Model, ORDEM2010
This paper describes the functionality and use of ORDEM2010, which replaces ORDEM2000, as the NASA Orbital Debris Program Office (ODPO) debris engineering model. Like its predecessor, ORDEM2010 serves the ODPO mission of providing spacecraft designers/operators and debris observers with a publicly available model to calculate orbital debris flux by current-state-of-knowledge methods. The key advance in ORDEM2010 is the input file structure of the yearly debris populations from 1995-2035 of sizes 10 micron - 1 m. These files include debris from low-Earth orbits (LEO) through geosynchronous orbits (GEO). Stable orbital elements (i.e., those that do not randomize on a sub-year timescale) are included in the files as are debris size, debris number, material density, random error and population error. Material density is implemented from ground-test data into the NASA breakup model and assigned to debris fragments accordingly. The random and population errors are due to machine error and uncertainties in debris sizes. These high-fidelity population files call for a much higher-level model analysis than what was possible with the populations of ORDEM2000. Population analysis in the ORDEM2010 model consists of mapping matrices that convert the debris population elements to debris fluxes. One output mode results in a spacecraft encompassing 3-D igloo of debris flux, compartmentalized by debris size, velocity, pitch, and yaw with respect to spacecraft ram direction. The second output mode provides debris flux through an Earth-based telescope/radar beam from LEO through GEO. This paper compares the new ORDEM2010 with ORDEM2000 in terms of processes and results with examples of specific orbits.
Krisko, Paula H.↗
Alignment and Scaling of Large-Scale Fluctuations in Solar Wind Turbulence
We investigate the dependence of solar wind fluctuations measured by the Wind spacecraft on scale and on the degree of alignment between oppositely directed Elsasser fields. This alignment controls the strength of the non-linear interactions and, therefore, the turbulence. We find that at scales larger than the outer scale of the turbulence the Elsasser fluctuations become on average more anti-aligned as the outer scale is approached from above. Conditioning their structure functions using the alignment angle reveals turbulent scaling of unaligned fluctuations at scales previously believed to lie outside the turbulent cascade in the '1/f range'. We argue that the 1/f range contains a mixture of non-interacting anti-aligned population of Alfven waves and magnetic force-free structures plus a subdominant population of unaligned cascading turbulent fluctuations.
Wicks, R. T.↗
Criteria for distinguishing biogenic and abiogenic amino acids - Preliminary considerations.
Criteria to determine the mode of origin of amino acids can be established by consideration of their structure, enantiometric distribution, composition, and relative abundance. A population of dominantly protein amino acids with one enantiomeric configuration most likely had a biological origin. Biological amino acids do racemize, however, so the absence of optical activity would not rule out the possibility that the amino acids in a racemic mixture were originally synthesized biologically. For racemic amino acids, therefore, structure, composition and relative abundance become important in ascertaining the origin of these compounds. Abiotically synthesized amino acids have a population composed of both protein and nonprotein structures present as racemic mixtures.
Kvenvolden, K. A.↗
Compartmentalization in proteinoid microspheres
Proteinoid microspheres with stable internal compartments and internal structure are made from acidic proteinoid and basic proteinoid with calcium. The populations of microspheres are characterized by a wide diversity of structure. A model of primitive intracellular communication is suggested by the observed movement of internal particles between compartments of a multicompartmentalized unit. Differential response to pH change and to temperature change has been demonstrated within one population and suggests one mode of adaptive selection among primordial cell populations.
Brooke, S.↗
Venus exospheric structure - The role of solar radiation pressure
The existence of a 'hot' population of hydrogen atoms in the Venus exosphere is well known. In the outer coronal region where it is dominant, r greater than about 2.0 R(V) (Venus radii), hydrogen atoms are also subject to a relatively strong radiation pressure exerted by resonant scattering of solar Lyman-alpha photons. Collisionless models illustrating the consequent structure are discussed, with the nonthermal population mimicked by a dual Maxwellian exobase kinetic distribution. In these models, a considerable fraction of the 'hot' atoms outside 2.0 R(V) belongs to the quasi-satellite component, this fraction exceeding 1/2 for r values between about 4.0 and 10.0 R(V). Solar ionization of bound atoms occurs mainly outside the ionopause, yielding a partial escape flux greater than about 2,000,000/sq cm per sec over the dayside exobase for assumed solar conditions. The inclusion of a cold exobase prescribed by Pioneer Venus observations has little influence on the outer region (in particular, the quasi-satellite component is unaltered) except that the transition to 'hot' kinetic character occurs closer to the exobase on the nightside due to the colder main exobase temperatures there.
Bishop, James↗
Galactic worms. I - Catalog of worm candidates
A catalog of candidates for the Galactic worms that are possibly the walls surrounding the superbubbles is compiled; 118 isolated structures that appear both in H I and in IR (60 and 100 microns). Fifty-two are possibly associated with H II regions. It is found that the 100-micron emissivity increases systematically toward the Galactic interior, which is consistent with the increase of the general interstellar radiation field. The 100-micron emissivity of the structures associated with the H II regions is larger than that of the structures without associated H II regions. The 60-100-micron ratio is large, 0.28 +/- 0.03, which may indicate that the grains associated with the atomic gas have a relatively large population of small grains. Thirty-five structures appear in the 408-MHz continuum. The IR and the radio continuum properties suggest that the 408-MHz continuum emission in those structures is very likely thermal. The implications of these results on the ionization of gas far from the Galactic plane are discussed.
Koo, Bon-Chul↗
The Stellar Imager (SI) - A Mission to Resolve Stellar Surfaces, Interiors, and Magnetic Activity
The Stellar Imager (SI) is a space-based, UV/Optical Interferometer (UVOI) designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and of the Universe in general. It will also probe via asteroseismology flows and structures in stellar interiors. SI will enable the development and testing of a predictive dynamo model for the Sun, by observing patterns of surface activity and imaging of the structure and differential rotation of stellar interiors in a population study of Sun-like stars to determine the dependence of dynamo action on mass, internal structure and flows, and time. SI's science focuses on the role of magnetism in the Universe and will revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magnetohydrodynamically controlled processes in the Universe. SI is a "LandmarklDiscovery Mission" in the 2005 Heliophysics Roadmap, an implementation of the UVOI in the 2006 Astrophysics Strategic Plan, and a NASA Vision Mission ("NASA Space Science Vision Missions" (2008), ed. M. Allen). We present here the science goals of the SI Mission, a mission architecture that could meet those goals, and the technology development needed to enable this mission
Christensen-Dalsgaard, Jorgen↗
Integrated Space Asset Management Database and Modeling
Effective Space Asset Management is one key to addressing the ever-growing issue of space congestion. It is imperative that agencies around the world have access to data regarding the numerous active assets and pieces of space junk currently tracked in orbit around the Earth. At the center of this issues is the effective management of data of many types related to orbiting objects. As the population of tracked objects grows, so too should the data management structure used to catalog technical specifications, orbital information, and metadata related to those populations. Marshall Space Flight Center's Space Asset Management Database (SAM-D) was implemented in order to effectively catalog a broad set of data related to known objects in space by ingesting information from a variety of database and processing that data into useful technical information. Using the universal NORAD number as a unique identifier, the SAM-D processes two-line element data into orbital characteristics and cross-references this technical data with metadata related to functional status, country of ownership, and application category. The SAM-D began as an Excel spreadsheet and was later upgraded to an Access database. While SAM-D performs its task very well, it is limited by its current platform and is not available outside of the local user base. Further, while modeling and simulation can be powerful tools to exploit the information contained in SAM-D, the current system does not allow proper integration options for combining the data with both legacy and new M&S tools. This paper provides a summary of SAM-D development efforts to date and outlines a proposed data management infrastructure that extends SAM-D to support the larger data sets to be generated. A service-oriented architecture model using an information sharing platform named SIMON will allow it to easily expand to incorporate new capabilities, including advanced analytics, M&S tools, fusion techniques and user interface for visualizations. In addition, tight control of information sharing policy will increase confidence in the system, which would encourage industry partners to provide commercial data. Combined with the integration of new and legacy M&S tools, a SIMON-based architecture will provide a robust environment that can be extended and expanded indefinitely.
MacLeod, Todd↗
Sensitivity analysis of physiological factors in space habitat design
The costs incurred by design conservatism in space habitat design are discussed from a structural standpoint, and areas of physiological research into less than earth-normal conditions that offer the greatest potential decrease in habitat construction and operating costs are studied. The established range of human tolerance limits is defined for those physiological conditions which directly affect habitat structural design. These entire ranges or portions thereof are set as habitat design constraints as a function of habitat population and degree of ecological closure. Calculations are performed to determine the structural weight and cost associated with each discrete population size and its selected environmental conditions, on the basis of habitable volume equivalence for four basic habitat configurations: sphere, cylinder with hemispherical ends, torus, and crystal palace.
Billingham, J.↗
The evolution of population II stars.
Evolutionary paths of several double energy-source models compared with horizontal branch in metal- weak Population II clusters to obtain stellar structure and mass for best fit
STELLAR STRUCTURE↗
Microbial ecology of extreme environments: Antarctic dry valley yeasts and growth in substrate limited habitats
The multiple stresses temperature, moisture, and for chemoheterotrophs, sources of carbon and energy of the Dry Valley Antarctica soils allow at best depauperate communities, low in species diversity and population density. The nature of community structure, the operation of biogeochemical cycles, the evolution and mechanisms of adaptation to this habitat are of interest in informing speculations upon life on other planets as well as in modeling the limits of gene life. Yeasts of the Cryptococcus vishniacil complex (Basidiobiastomycetes) are investigated, as the only known indigenes of the most hostile, lichen free, parts of the Dry Valleys. Methods were developed for isolating these yeasts (methods which do not exclude the recovery of other microbiota). The definition of the complex was refined and the importance of nitrogen sources was established as well as substrate competition in fitness to the Dry Valley habitats.
Vishniac, H. S.↗