2,919 research outputs found
Software development tools: A bibliography, appendix C.
A bibliography containing approximately 200 citations on tools which help software developers perform some development task (such as text manipulation, testing, etc.), and which would not necessarily be found as part of a computing facility is given. The bibliography comes from a relatively random sampling of the literature and is not complete. But it is indicative of the nature and range of tools currently being prepared or currently available
Software development environments: A bibliography, appendix G
A bibliography containing approximately 100 citations on software development environments is given. The bibliography comes from a relatively random sampling of the literature and is not complete
Software development environments: Present and future, appendix D
Computerized environments which facilitate the development of appropriately functioning software systems are discussed. Their current status is reviewed and several trends exhibited by their history are identified. A number of principles, some at (slight) variance with the historical trends, are suggested and it is argued that observance of these principles is critical to achieving truly effective and efficient software development support environments
LaRC local area networks to support distributed computing
The Langley Research Center's (LaRC) Local Area Network (LAN) effort is discussed. LaRC initiated the development of a LAN to support a growing distributed computing environment at the Center. The purpose of the network is to provide an improved capability (over inteactive and RJE terminal access) for sharing multivendor computer resources. Specifically, the network will provide a data highway for the transfer of files between mainframe computers, minicomputers, work stations, and personal computers. An important influence on the overall network design was the vital need of LaRC researchers to efficiently utilize the large CDC mainframe computers in the central scientific computing facility. Although there was a steady migration from a centralized to a distributed computing environment at LaRC in recent years, the work load on the central resources increased. Major emphasis in the network design was on communication with the central resources within the distributed environment. The network to be implemented will allow researchers to utilize the central resources, distributed minicomputers, work stations, and personal computers to obtain the proper level of computing power to efficiently perform their jobs
An assessment of DREAM, appendix E
The design realization, evaluation and modelling (DREAM) system is evaluated. A short history of the DREAM research project is given as well as the significant characteristics of DREAM as a development environment. The design notation which is the basis for the DREAM system is reviewed, and the development tools envisioned as part of DREAM are discussed. Insights into development environments and their production are presented and used to make suggestions for future work in the area of development environments
Software development environment, appendix F
The current status in the area of software development environments is assessed. The purposes of environments, the types of environments, the constituents of an environment, the issue of environment integration, and the problems which must be solved in preparing an environment are discussed. Some general maxims to guide near-term future work are proposed
The pulsation modes of the pre-white dwarf PG 1159-035
Context. PG 1159-035, a pre-white dwarf with T_(eff) ≃ 140 000 K, is the prototype of both two classes: the PG 1159 spectroscopic class and the DOV pulsating class. Previous studies of PG 1159-035 photometric data obtained with the Whole Earth Telescope (WET) showed a rich frequency spectrum allowing the identification of 122 pulsation modes. Analyzing the periods of pulsation, it is possible to measure the stellar mass, the rotational period and the inclination of the rotation axis, to estimate an upper limit for the magnetic field, and even to obtain information about the inner stratification of the star.
Aims. We have three principal aims: to increase the number of detected and identified pulsation modes in PG 1159-035, study trapping of the star's pulsation modes, and to improve or constrain the determination of stellar parameters.
Methods. We used all available WET photometric data from 1983, 1985, 1989, 1993 and 2002 to identify the pulsation periods.
Results. We identified 76 additional pulsation modes, increasing to 198 the number of known pulsation modes in PG 1159-035, the largest number of modes detected in any star besides the Sun. From the period spacing we estimated a mass M/M_⊙ = 0.59 ± 0.02 for PG 1159-035, with the uncertainty dominated by the models, not the observation. Deviations in the regular period spacing suggest that some of the pulsation modes are trapped, even though the star is a pre-white dwarf and the gravitational settling is ongoing. The position of the transition zone that causes the mode trapping was calculated at r_c/R_* = 0.83 ± 0.05. From the multiplet splitting, we calculated the rotational period P_(rot) = 1.3920 ± 0.0008 days and an upper limit for the magnetic field, B < 2000 G. The total power of the pulsation modes at the stellar surface changed less than 30% for ℓ = 1 modes and less than 50% for ℓ = 2 modes. We find no evidence of linear combinations between the 198 pulsation mode frequencies. PG 1159-035 models have not significative convection zones, supporting the hypothesis that nonlinearity arises in the convection zones in cooler pulsating white dwarf stars
Flight software requirements and design support system
The desirability and feasibility of computer-augmented support for the pre-implementation activities occurring during the development of flight control software was investigated. The specific topics to be investigated were the capabilities to be included in a pre-implementation support system for flight control software system development, and the specification of a preliminary design for such a system. Further, the pre-implementation support system was to be characterized and specified under the constraints that it: (1) support both description and assessment of flight control software requirements definitions and design specification; (2) account for known software description and assessment techniques; (3) be compatible with existing and planned NASA flight control software development support system; and (4) does not impose, but may encourage, specific development technologies. An overview of the results is given
Sensitivity to hydrocarbons and cytochrome P4501A enzyme activity in Arctic marine birds and waterfowl
Thesis (M.S.) University of Alaska Fairbanks, 2017The Arctic is host to a taxonomically diverse group of birds, including species of conservation and subsistence importance that spend many months of their annual cycle in the region. With prospects for oil and gas resource development and increases in vessel traffic in the Beaufort and Chukchi Seas, arctic birds could be valuable bioindicators to monitor contaminants and specifically hydrocarbons from crude oil. Using liver cytochrome P4501A (CYP1A) activity, I measured levels of hydrocarbon exposure in three bird species of subsistence importance: king eiders (Somateria spectabilis), common eiders (Somateria mollissima), and greater white-fronted geese (Anser albifrons). Over the course of three years, I collected liver samples during spring and fall hunts near Utqiaġvik (formally Barrow) and validated methods for both direct-take and opportunistic liver sampling. Enzyme activity results show significant differences in CYP1A activity levels among species, seasons, and years. Except birds collected during fall 2014, when significantly high enzyme activity was observed in all sampled species, all other collections resulted in median activity levels similar to those reported in other sea duck species in Alaska from un-oiled or non-industrialized habitats. I also used species-specific hepatocyte culture in a broader selection of arctic marine birds and waterfowl candidate bioindicators to assess and compare species CYP1A activity responses as a measure of sensitivity to hydrocarbons. Cytochrome P4501A results from hepatocyte cultures dosed with positive control reference reagents and Alaska North Slope crude oil showed differences in species responses. Based on sensitivity results, I recommend the common eider and common murre (Uria aalge) as bioindicators for use in CYP1A monitoring due to their consistent and measureable responses in our experiments. However, additional species are promising candidates (e.g., tufted puffin; Fratercula cirrhata) but further testing is needed. This is the first study of reference hydrocarbon exposure and comparative laboratory assessment of CYP1A inducing compounds for arctic marine birds and waterfowl and these results form the basis for hydrocarbon monitoring programs and risk assessments
Impact of historical climate change on the genetic structure of the Great Basin Pocket Mouse, Perognathus parvus
The dynamics of genetic patterns, such as genetic differentiation within and between populations and the geographic distribution of genetic lineages, are often influenced by historical events (such as climatic changes) that have substantially impacted regional biodiversity (the study of phylogeography; Avise, 20001). The magnitude of genetic differentiation among populations is often increased if suitable habitat is reduced, because there is restricted migration among populations. When migration is restricted, the populations may become genetically differentiated from conspecific populations and, over time, may become independent lineages that follow distinctive evolutionary trajectories (Stebbins, 19523; Nevo & Beiles, 19892; Thomas et al., 19984). In particular, glacial cycles often result in expansion and contraction of suitable habitat for organisms, which we might predict leads to a similar expansion and contraction of organismal populations. Understanding the impact of past glacial-interglacial cycles (Figure 1), and thus climate changes, on species and species assemblages can help us understand what we may expect from current and future climate change trends
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