Integrated problem solving environment: the SCIRun computational steering system

Journal ArticleSCIRun is a scientific programming environment that allows the interactive construction, debugging, and steering of large-scale scientific computations. We review related systems and introduce a taxonomy that explores different computational steering solutions, Considering these approaches, we discuss why a tightly integrated problem solving environment, such as SCIRun, simplifies the design and debugging phases of computational science applications and how such an environment aids in the scientific discovery process

Feasibility study of an Integrated Program for Aerospace vehicle Design (IPAD). Volume 1A: Summary

IPAD was defined as a total system oriented to the product design process. This total system was designed to recognize the product design process, individuals and their design process tasks, and the computer-based IPAD System to aid product design. Principal elements of the IPAD System include the host computer and its interactive system software, new executive and data management software, and an open-ended IPAD library of technical programs to match the intended product design process. The basic goal of the IPAD total system is to increase the productivity of the product design organization. Increases in individual productivity were feasible through automation and computer support of routine information handling. Such proven automation can directly decrease cost and flowtime in the product design process

A Two-Fluid Thermally-Stable Cooling Flow Model

A new model for cooling flows in X-ray clusters, capable of naturally explaining salient features observed, is proposed. The only requirement is that a significant relativistic component, in the form of cosmic rays (CR), be present in the intra-cluster medium and significantly frozen to the thermal gas. Such an addition qualitatively alters the conventional isobaric thermal instability criterion such that a fluid parcel becomes thermally stable when its thermal pressure drops below a threshold fraction of its CR pressure. Consequently, the lowest possible temperature at any radius is about one third of the ambient temperature {\it at that radius}, exactly as observed, In addition, we suggest that dissipation of internal gravity waves, excited by radial oscillatory motions of inward drifting cooling clouds about their radial equilibrium positions, may be responsible for heating up cooling gas. With the ultimate energy source for powering the cooling X-ray luminosity and heating up cooling gas being gravitational due to inward drifting cooling clouds as well as the general inward flow, heating is spatially distributed and energetically matched with cooling. One desirable property of this heating mechanism is that heating energy is strongly centrally concentrated, providing the required heating for emission-line nebulae.Comment: 13 pages, submitted to ApJ

Shell structure and electron-electron interaction in self-assembled InAs quantum dots

Using far-infrared spectroscopy, we investigate the excitations of self-organized InAs quantum dots as a function of the electron number per dot, 1<n<6, which is monitored in situ by capacitance spectroscopy. Whereas the well-known two-mode spectrum is observed when the lowest s - states are filled, we find a rich excitation spectrum for n=3, which reflects the importance of electron-electron interaction in the present, strongly non-parabolic confining potential. From capacitance spectroscopy we find that the electronic shell structure in our dots gives rise to a distinct pattern in the charging energies which strongly deviates from the monotonic behavior of the Coulomb blockade found in mesoscopic or metallic structures.Comment: 4 pages, 3 PostScript figure

Scaling and Universality in City Space Syntax: between Zipf and Matthew

We report about universality of rank-integration distributions of open spaces in city space syntax similar to the famous rank-size distributions of cities (Zipf's law). We also demonstrate that the degree of choice an open space represents for other spaces directly linked to it in a city follows a power law statistic. Universal statistical behavior of space syntax measures uncovers the universality of the city creation mechanism. We suggest that the observed universality may help to establish the international definition of a city as a specific land use pattern.Comment: 24 pages, 5 *.eps figure

Genetic Progress From 50 Years of Smooth Bromegrass Breeding

Since its introduction from Eurasia, smooth bromegrass (Bromus inermis Leyss.) has become an important cool-season forage grass in North America. The objective of this study was to document breeding progress in smooth bromegrass between 1942 and 1995 in North America. Thirty cultivars or experimental populations were tested at up to seven sites in the eastern and central USA, with a range of soil types and climates. There have been small genetic changes in forage yield, brown leafspot resistance [caused by Pyrenophora bromi (Died) Drechs.], in vitro dry matter digestibility (IVDMD), and neutral detergent fiber (NDF) concentration. Brown leafspot resistance increased gradually, averaging 0.21 units decade(-1). Mean forage yield did not change for cultivars developed after 1942, but was 0.54 Mg ha(-1) (7.2%) higher for the post-1942 group than in \u27Lincoln\u27, a direct representative of smooth bromegrass introduced into North America. Selection for increased IVDMD led to an average increase in IVDMD of 9 g kg(-1) (1.4%), an increase in forage yield of 0.33 Mg ha(-1) (5.0%), and a decrease in NDF of -8 g kg(-1) (-1.2%) in the post-1942 group. The slow rate of progress for smooth bromegrass forage yield is due to its complex polypoid inheritance, emphasis on traits other than forage yield, and relatively little concentrated attention from public and private breeders

Latitudinal and Longitudinal Adaptation of Smooth Bromegrass Populations

Breeding progress has been slow in smooth bromegrass (Bromus inermis Leyss) since its introduction to North America. Much of the variability among cultivars appears to have arisen by natural selection and adaptive responses. The objective of this study was to determine if smooth bromegrass cultivars differ in latitudinal or longitudinal adaptation, as measured by forage yield, and if that variability relates to their breeding or selection history. The target region was defined as the Great Plains to the East Coast of the USA, from 38 to 47 degrees N latitude. Twenty-nine cultivars and experimental populations were evaluated for forage yield at up to seven locations ranging from central to eastern USA. Populations were classified according to pooled population main effect and population x location interaction effect (G + GL deviations). Cluster analysis resulted in eight clusters that explained 90% of the variation among G + GL deviations. One cluster consisted of populations average in adaptation, four clusters consisted of populations that were largely unadapted across the entire region, and three clusters consisted of populations that were specifically adapted to the entire region or a large part thereof. Much of the grouping and adaptation characteristics could be explained by similar pedigrees, selection history, and selection location. However, the phenotypic similarity of some superior, but divergent-pedigree populations suggested that alleles for high and stable forage yield in smooth bromegrass probably exist in numerous germplasm sources. Despite a history of little to no gains in forage yield, these results suggest unrealized potential for future improvement of forage yield of smooth bromegrass across a broad geographic region

Outer boundary conditions for evolving cool white dwarfs

White dwarf evolution is essentially a gravothermal cooling process, which,for cool white dwarfs, sensitively depends on the treatment of the outer boundary conditions. We provide detailed outer boundary conditions appropriate for computing the evolution of cool white dwarfs employing detailed non-gray model atmospheres for pure H composition. We also explore the impact on the white dwarf cooling times of different assumptions for energy transfer in the atmosphere of cool white dwarfs. Detailed non-gray model atmospheres are computed taken into account non-ideal effects in the gas equation of state and chemical equilibrium, collision-induced absorption from molecules, and the Lyman alpha quasi-molecular opacity. Our results show that the use of detailed outer boundary conditions becomes relevant for effective temperatures lower than 5800 and 6100K for sequences with 0.60 and 0.90 M_sun, respectively. Detailed model atmospheres predict ages that are up to approx 10% shorter at log L/L_sun=-4 when compared with the ages derived using Eddington-like approximations at tau_Ross=2/3. We also analyze the effects of various assumptions and physical processes of relevance in the calculation of outer boundary conditions. In particular, we find that the Ly_alpha red wing absorption does not affect substantially the evolution of white dwarfs. White dwarf cooling timescales are sensitive to the surface boundary conditions for T_eff < 6000K. Interestingly enough, non-gray effects have little consequences on these cooling times at observable luminosities. In fact, collision-induced absorption processes, which significantly affect the spectra and colors of old white dwarfs with hydrogen-rich atmospheres, have not noticeable effects in their cooling rates, except throughout the Rosseland mean opacity.Comment: 6 pages, 9 figures, to be published in Astronomy and Astrophysic

Gravitational Radiation from Intermediate-Mass Black Holes

Recent X-ray observations of galaxies with ROSAT, ASCA, and Chandra have revealed numerous bright off-center point sources which, if isotropic emitters, are likely to be intermediate-mass black holes, with hundreds to thousands of solar masses. The origin of these objects is under debate, but observations suggest that a significant number of them currently reside in young high-density stellar clusters. There is also growing evidence that some Galactic globular clusters harbor black holes of similar mass, from observations of stellar kinematics. In such high-density stellar environments, the interactions of intermediate-mass black holes are promising sources of gravitational waves for ground-based and space-based detectors. Here we explore the signal strengths of binaries containing intermediate-mass black holes or stellar-mass black holes in dense stellar clusters. We estimate that a few to tens per year of these objects will be detectable during the last phase of their inspiral with the advanced LIGO detector, and up to tens per year will be seen during merger, depending on the spins of the black holes. We also find that if these objects reside in globular clusters then tens of sources will be detectable with LISA from the Galactic globular system in a five year integration, and similar numbers will be detectable from more distant galaxies. The signal strength depends on the eccentricity distribution, but we show that there is promise for strong detection of pericenter precession and Lense-Thirring precession of the orbital plane. We conclude by discussing what could be learned about binaries, dense stellar systems, and strong gravity if such signals are detected.Comment: Minor changes, accepted by ApJ (December 10, 2002

The multiple planets transiting Kepler-9 I. Inferring stellar properties and planetary compositions

The discovery of multiple transiting planetary systems offers new possibilities for characterising exoplanets and understanding their formation. The Kepler-9 system contains two Saturn-mass planets, Kepler-9b and 9c. Using evolution models of gas giants that reproduce the sizes of known transiting planets and accounting for all sources of uncertainties, we show that Kepler-9b (respectively 9c) contains $45^{+17}_{-12}$\,\mearth\ (resp. $31^{+13}_{-10}$\,\mearth) of hydrogen and helium and $35^{+10}_{-15}$\,\mearth (resp. $24^{+10}_{-12}$\,\mearth) of heavy elements. More accurate constraints are obtained when comparing planets 9b and 9c: the ratio of the total mass fractions of heavy elements are $Z_{\rm b}/Z_{\rm c}=1.02\pm 0.14$, indicating that, although the masses of the planets differ, their global composition is very similar, an unexpected result for formation models. Using evolution models for super-Earths, we find that Kepler-9d must contain less than 0.1% of its mass in hydrogen and helium and predict a mostly rocky structure with a total mass between 4 and 16\,\mearth.Comment: 5 pages + 7 pages of online material ; revised article submitted to A\&A and accepted on March 3