3,823 research outputs found
Arecibo Multi-Epoch HI Absorption Measurements Against Pulsars: Tiny-Scale Atomic Structure
We present results from multi-epoch neutral hydrogen (HI) absorption
observations of six bright pulsars with the Arecibo telescope. Moving through
the interstellar medium (ISM) with transverse velocities of 10--150 AU/yr,
these pulsars have swept across 1--200 AU over the course of our experiment,
allowing us to probe the existence and properties of the tiny scale atomic
structure (TSAS) in the cold neutral medium (CNM). While most of the observed
pulsars show no significant change in their HI absorption spectra, we have
identified at least two clear TSAS-induced opacity variations in the direction
of B1929+10. These observations require strong spatial inhomogeneities in
either the TSAS clouds' physical properties themselves or else in the clouds'
galactic distribution. While TSAS is occasionally detected on spatial scales
down to 10 AU, it is too rare to be characterized by a spectrum of turbulent
CNM fluctuations on scales of 10-1000 AU, as previously suggested by some work.
In the direction of B1929+10, an apparent correlation between TSAS and
interstellar clouds inside the warm Local Bubble (LB) indicates that TSAS may
be tracing the fragmentation of the LB wall via hydrodynamic instabilities.
While similar fragmentation events occur frequently throughout the ISM, the
warm medium surrounding these cold cloudlets induces a natural selection effect
wherein small TSAS clouds evaporate quickly and are rare, while large clouds
survive longer and become a general property of the ISM.Comment: 21 pages, 13 figures, accepted by Ap
Curation and preservation of complex data: North Carolina Geospatial Data Archiving Project
The North Carolina Geospatial Data Archiving Project (NCGDAP) is a three-year joint effort of the North Carolina State University Libraries and the North Carolina Center for Geographic Information and Analysis focused on collection and preservation of digital geospatial data resources from state and local government agencies. CGDAP is being undertaken in partnership with the Library of Congress under the ational Digital Information Infrastructure and Preservation Program (NDIIPP). “Digital geospatial data” consists of digital information that identifies the geographic location and characteristics of natural or constructed features and boundaries on the earth. Such data resources include geographic information systems (GIS) data sets, digitized maps, remote sensing data resources such as digital aerial photography, and tabular data that are tied to specific locations. These complex data objects do not suffer well from neglect, and long-term preservation will involve some combination of format migration and retention of critical documentation. While the main focus of NCGDAP is on organizational issues related to the engagement of spatial data infrastructure in the process of data archiving--with the demonstration repository seen more as a catalyst for discussion rather than an end in itself--this paper focuses more narrowly on the technical challenges associated with eveloping an ingest workflow and archive development process. New preservation hallenges associated with emergent content forms are also resented
Mission analysis of solar powered aircraft
The effect of a real mission scenario on a solar powered airplane configuration which had been developed in previous work were assessed. The mission used was surveillance of crop conditions over a route from Phoenix to Tucson to Tombstone, Arizona. Appendices are attached which address the applicability of existing platforms and payloads to do this mission
Multiple Signaling Functions Of Song In A Polymorphic Species With Alternative Reproductive Strategies
Vocal traits can be sexually selected to reflect male quality, but may also evolve to serve additional signaling functions. We used a long-term dataset to examine the signaling potential of song in dimorphic white-throated sparrows (Zonotrichia albicollis). We investigated whether song conveys multifaceted information about the vocalizing individual, including fitness, species identity, individual identity, and morph. We also evaluated whether song traits correlate differently with fitness in the two morphs, as the more promiscuous strategy of white, relative to tan, morph males might impose stronger sexual selection. Males with high song rates achieved higher lifetime reproductive success, and this pattern was driven by white morph males. In addition, males that sang songs with many notes survived longer, but this pattern was less robust. Thus, song traits reflect differences in fitness and may more strongly affect fitness in the white morph. Song frequency was unrelated to fitness, body size, or morph, but was individual specific and could signal individual identity. Songs of the two morphs displayed similar frequency ratios and bandwidths. However, tan morph males sang songs with longer first notes, fewer notes, and higher variability. Thus, song could be used in morph discrimination. Variation in frequency ratios between notes was low and could function in conspecific recognition, but pitch change dynamics did differ between four different song types observed. Our results support a multiple messages model for white-throated sparrow song, in which different song traits communicate discrete information about the vocalizing individual
Rapid method for determination of antimicrobial susceptibilities pattern of urinary bacteria
Method determines bacterial sensitivity to antimicrobial agents by measuring level of adenosine triphosphate remaining in the bacteria. Light emitted during reaction of sample with a mixture of luciferase and luciferin is measured
Problem areas in the use of the firefly luciferase assay for bacterial detection
By purifying the firefly luciferase extract and adding all necessary chemicals but ATP in excess, an assay for ATP was performed by measuring the amount of light produced when a sample containing soluble ATP is added to the luciferase reaction mixture. Instrumentation, applications, and basic characteristics of the luciferase assay are presented. Effect of the growth medium and length of time grown in this medium on ATP per viable E. coli values is shown in graphic form, along with an ATP concentration curve showing relative light units versus ATP injected. Reagent functions and concentration methods are explored. Efforts to develop a fast automatable system to detect the presence of bacteria in biological fluids, especially urine, resulted in the optimization of procedures for use with different types of samples
Application of firefly luciferase assay for adenosine triphosphate (ATP) to antimicrobial drug sensitivity testing
The development of a rapid method for determining microbial susceptibilities to antibiotics using the firefly luciferase assay for adenosine triphosphate (ATP) is documented. The reduction of bacterial ATP by an antimicrobial agent was determined to be a valid measure of drug effect in most cases. The effect of 12 antibiotics on 8 different bacterial species gave a 94 percent correlation with the standard Kirby-Buer-Agar disc diffusion method. A 93 percent correlation was obtained when the ATP assay method was applied directly to 50 urine specimens from patients with urinary tract infections. Urine samples were centrifuged first to that bacterial pellets could be suspended in broth. No primary isolation or subculturing was required. Mixed cultures in which one species was predominant gave accurate results for the most abundant organism. Since the method is based on an increase in bacterial ATP with time, the presence of leukocytes did not interfere with the interpretation of results. Both the incubation procedure and the ATP assays are compatible with automation
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