14,738 research outputs found
IUE and IRAS observations of luminous M stars with varying gas-to dust ratios
Circumstellar gas and dust surrounding M giants and supergiants show luminous M stars to split into two distinct classes. Stars with a high gas to dust ratio all show chromospheric Ca II, H, and K emission. Stars with a high dust to gas ratio do not show chromospheric Ca II emission but are the only ones to show Balmer emission indicative of atmospheric shocks and are also the only ones to show maser emission. In order to determine whether all chromospheric indicators disappear in high dust to gas ratio stars, a survey of stars in both these classes was conducted with the IUE satellite. Long wavelength infrared fluxes for the program stars were obtained from the IRAS point source catalog. There is no obvious difference in the long wavelength observations between the two groups of stars. The long wavelength excess tends to follow the 10 micron excess and not the dust to gas ratio
Strapdown inertial measurement unit computer, volume 1 Final report
Strapdown inertial measurement unit design, calculations, and operating instruction
Prior accounting knowledge of first-year students at two South African universities: Contributing factor to academic performance or not?
Factors that influence studentsā academic performance are important for higher education institutions, students and professional bodies. This study focuses on the prior accounting knowledge of students entering higher education, one of the factors that could influence studentsā success. The reasons for revisiting this factor are firstly, admission requirements for students applying for the Bachelor of Commerce (BCom) in Accounting degree are different among South African universities regarding Accounting as a pre-requisite school subject; secondly, Grade 12 subjects have changed significantly with the introduction of the National Senior Certificate (NSC) examination in 2008; and lastly, comparing studentsā prior accounting knowledge as a contributing factor or not of international studies with South African studies. The purpose of this study was to investigate the effect on first-year Accounting studentsā academic performance whether they had or did not have Accounting as a school subject for students enrolled for an Accounting degree at two South African universities. The research method used a quantitative methodology. The findings of the study offer a better understanding of and a greater sensitivity for studentsā prior knowledge which might influence their academic performance. The value of the study is an important contribution to the consideration of admission requirements for students applying for an Accounting degree at South African universities
Evidence for Mass-dependent Circumstellar Disk Evolution in the 5 Myr Old Upper Scorpius OB Association
We present 4.5, 8, and 16 Āµm photometry from the Spitzer Space Telescope for 204 stars in the Upper Scorpius OB
association. The data are used to investigate the frequency and properties of circumstellar disks around stars with masses between ~0.1 and 20 M_ā at an age of ~5 Myr. We identify 35 stars that have emission at 8 or 16 Āµm in excess of the, stellar photosphere. The lower mass stars (~0.1ā1.2M_ā) appear surrounded by primordial optically thick disks based on, the excess emission characteristics. Starsmoremassive than ~1.8M_ā have lower fractional excess luminosities suggesting, that the inner ~10 AU of the disk has been largely depleted of primordial material. None of the G and F stars (~1.2ā1.8 M_ā) in our sample have an infrared excess at wavelengths ā¤16 Āµm. These results indicate that the mechanisms for, dispersing primordial optically thick disks operate less efficiently, on average, for low-mass stars, and that longer timescales are available for the buildup of planetary systems in the terrestrial zone for stars with masses ā¾1 M_ā
Brain neurons as quantum computers: {\it in vivo} support of background physics
The question: whether quantum coherent states can sustain decoherence,
heating and dissipation over time scales comparable to the dynamical timescales
of the brain neurons, is actively discussed in the last years. Positive answer
on this question is crucial, in particular, for consideration of brain neurons
as quantum computers. This discussion was mainly based on theoretical
arguments. In present paper nonlinear statistical properties of the Ventral
Tegmental Area (VTA) of genetically depressive limbic brain are studied {\it in
vivo} on the Flinders Sensitive Line of rats (FSL). VTA plays a key role in
generation of pleasure and in development of psychological drug addiction. We
found that the FSL VTA (dopaminergic) neuron signals exhibit multifractal
properties for interspike frequencies on the scales where healthy VTA
dopaminergic neurons exhibit bursting activity. For high moments the observed
multifractal (generalized dimensions) spectrum coincides with the generalized
dimensions spectrum calculated for a spectral measure of a {\it quantum} system
(so-called kicked Harper model, actively used as a model of quantum chaos).
This observation can be considered as a first experimental ({\it in vivo})
indication in the favour of the quantum (at least partially) nature of the
brain neurons activity
Recognition of 3-D Objects from Multiple 2-D Views by a Self-Organizing Neural Architecture
The recognition of 3-D objects from sequences of their 2-D views is modeled by a neural architecture, called VIEWNET that uses View Information Encoded With NETworks. VIEWNET illustrates how several types of noise and varialbility in image data can be progressively removed while incornplcte image features are restored and invariant features are discovered using an appropriately designed cascade of processing stages. VIEWNET first processes 2-D views of 3-D objects using the CORT-X 2 filter, which discounts the illuminant, regularizes and completes figural boundaries, and removes noise from the images. Boundary regularization and cornpletion are achieved by the same mechanisms that suppress image noise. A log-polar transform is taken with respect to the centroid of the resulting figure and then re-centered to achieve 2-D scale and rotation invariance. The invariant images are coarse coded to further reduce noise, reduce foreshortening effects, and increase generalization. These compressed codes are input into a supervised learning system based on the fuzzy ARTMAP algorithm. Recognition categories of 2-D views are learned before evidence from sequences of 2-D view categories is accumulated to improve object recognition. Recognition is studied with noisy and clean images using slow and fast learning. VIEWNET is demonstrated on an MIT Lincoln Laboratory database of 2-D views of jet aircraft with and without additive noise. A recognition rate of 90% is achieved with one 2-D view category and of 98.5% correct with three 2-D view categories.National Science Foundation (IRI 90-24877); Office of Naval Research (N00014-91-J-1309, N00014-91-J-4100, N00014-92-J-0499); Air Force Office of Scientific Research (F9620-92-J-0499, 90-0083
Direct UV observations of the circumstellar envelope of alpha Orionis
Observations were made in the IUE LWP camera, low dispersion mode, with alpha Ori being offset various distances from the center of the Long Wavelength Large Aperture along its major axis. Signal was acquired at all offset positions and is comprised of unequal components of background/dark counts, telescope-scattered light, and scattered light emanating from the extended circumstellar shell. The star is known from optical and infrared observations to possess an extended, arc-minute sized, shell of cool material. Attempts to observe this shell with the IUE are described, although the deconvolution of the stellar signal from the telescope scattered light requires further calibration effort
IV. Fossil Fishes From The Miocene Ellensburg Formation, South Central Washington
The Ellensburg Formation was named for sediments deposited in the Kittitas Valley along the Yakima River near Ellensburg, Washington (Russell, 1893, 1900). Similar beds are present to the south along the leeward front of the emerging central Cascade Mountains; including the Nile, Selah, Yakima, and Toppenish basins. Further south along the Columbia River, portions of the Dalles Group, Rhododendron Formation, and Sandy River Mudstone are likely temporal equivalents; the latter two of which are found on the windward side of the uplifting Cascade Range (Farooqui, et al., 1981; Evarts et al., 2009).Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146545/1/MP 204vol4.pdfDescription of MP 204vol4.pdf : Main Articl
Physicochemical Properties and Catalytic Behavior of the Molecular Sieve SSZ-70
SSZ-70 is synthesized using 1,3-bis(isobutyl)imidazolium, 1,3-bis(cyclohexyl)imidazolium, and 1,3-bis(cycloheptyl)imidazolium structure directing agents (SDAs), and the solids obtained are characterized by powder X-ray diffraction (XRD), ^(29)Si magic angle spinning nuclear magnetic resonance (MAS NMR), electron microscopy, nitrogen and hydrocarbon adsorption, and thermogravimetric analyses. The physicochemical properties of SSZ-70 show that it is a new molecular sieve that has similarities to MWW-type materials. The catalytic behavior of SSZ-70 is evaluated through the use of the constraint index (CI) test. Distinct differences in the reactivity between Al-SSZ-70 and SSZ-25 (MWW) are observed and are the consequences of the structural differences between these two molecular sieves
Fossil And Recent Mountain Suckers, Pantosteus, And Significance Of Introgression In Catostomin Fishes Of Western United States
Catostomus is the most diverse genus of fishes in western North America. Over thirty species of Catostomus and other catostomins have been classified in five recent genera, Catostomus, Deltistes, Chasmistes, Xyrauchen, and Pantosteus. Introgressed evolutionary history is apparent in all five western catostomin genera. Mountain suckers, subgenus Pantosteus, are small and medium-sized fishes that live in moderate-gradient streams in the foothills and mountains, from the Black Hills to Pacific coastal drainages and from western Canada to central Mexico. Pantosteus is distinct in its molecular as well as morphological traits, but it is polyphyletic because Catostomus (Pantosteus) columbianus shares unique, derived morphological traits with Pantosteus and mtDNA with Catostomus (s.s.), thereby identifying two genera in its ancestry. We recognize three subgroups of Pantosteus: C. (P.) discobolus group of six species is distributed in the Snake River, eastern and southern Basin and Range Province to central Mexico, the Colorado Plateau, and the Los Angeles Basin. The C. (P.) platyrhynchus species group consists of four species, found in the Columbia, Snake, Upper Missouri, Upper Green, Lahontan, and Bonneville basins. Catostomus (P.) columbianus is a separate subgroup. The Pantosteus fossil record is sparse. We describe three Miocene records of the C. (P.) discobolus group from Oregon and Washington, three Pliocene species from Idaho and Nevada, and two Pleistocene records--from the Rio Grande rift in Colorado and from the Missouri River drainage of Kansas. The Kansas record suggests a much wider range for the species during glacial periods. Miocene relatives of C. (P.) discobolus from three sites in Oregon and Washington, 11.5-8.5 million years old, are morphologically advanced suckers. The Pliocene species from southern Nevada is intermediate between its modern relatives in the surrounding Great Basin and Colorado Plateau. At least one of the two Pliocene mountain suckers in the Snake River drainage was probably involved in the hybrid ancestry of C. (P.) columbianus. The general Pantosteus pattern suggests an origin in the northwest Great Basin and Columbia Plateau, with a history of dispersal, isolation, and evolution southward through Basin and Range drainages to the Colorado Plateau and Mexico, and eastward across the Rocky Mountains to the Missouri drainage. Mountain suckers are adapted to moderate-gradient mountain streams and to scraping food from rocky substrate.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/122717/1/OP 743.pd
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