5,693 research outputs found
Machine Science in Biomedicine: Practicalities, Pitfalls and Potential
Machine Science, or Data-driven Research, is a new and interesting scientific
methodology that uses advanced computational techniques to identify, retrieve,
classify and analyse data in order to generate hypotheses and develop models.
In this paper we describe three recent biomedical Machine Science studies, and
use these to assess the current state of the art with specific emphasis on data
mining, data assessment, costs, limitations, skills and tool support
Some Bright Stars with Smooth Continua for Calibrating the Response of High Resolution Spectrographs
When characterizing a high resolution echelle spectrograph, for instance for
precise Doppler work, it is useful to observe featureless sources such as
quartz lamps or hot stars to determine the response of the instrument. Such
sources provide a way to determine the blaze function of the orders,
pixel-to-pixel variations in the detector, fringing in the system, and other
important characteristics. In practice, however, many B or early A stars do not
provide a smooth continuum, whether because they are not rotating rapidly
enough or for some other reason. In fact, we have found that published
rotational velocities and temperatures are not a specific and sensitive guide
to whether a star's continuum will be smooth. A useful resource for observers,
therefore, is a list of "good" hot stars: bright, blue stars known empirically
to have no lines or other spectral features beyond the Balmer series with
minima below 95% of the continuum.
We have compiled a list of such stars visible from Northern Hemisphere
telescopes. This list includes all stars listed in the Yale Bright Star Catalog
(Hoffleit & Jaschek 1991) as being single with V 175 km/s, and
declination > -30, and many other hot stars that we have found useful for
calibration purposes.
The list here of "bad" stars may also be of interest in studies of hot,
slowly rotating stars
The Prevalence of Pulmonary and Upper Respiratory Tract Symptoms and Spirometric Test Findings Among Newspaper Pressroom Workers Exposed to Solvents
To investigate the relationship between exposure to organic solvents and the presence of pulmonary and upper respiratory tract mucous membrane symptoms, we conducted a cross-sectional study of 215 newspaper pressroom workers who were occupationally exposed to organic solvent and lubricant mixtures. Thirty-four compositors, who were not occupationally exposed to the solvents or lubricants, served as controls. Pressroom workers and compositors underwent spirometric testing and were also asked about the presence of cough, phlegm, hemoptysis, dyspnea, wheezing, chest tightness, nose or throat irritation, eye irritation, and sinus trouble. The spirometric results did not significantly differ between the two groups. However, the pressroom workers were significantly more likely to report pulmonary or upper respiratory tract mucous membrane symptoms than were compositors (P \u3c 0.005). An exposure-response relationship could be demonstrated when comparing the number of solvents exposed with the total number of symptoms (P \u3c 0.001). Similarly, an exposure-response relationship could be demonstrated when comparing the frequency of use of each of the seven solvents with the total number of symptoms (P \u3c 0.002). Each of these findings was supported in a multivariable linear regression model that adjusted for potential confounders such as age, smoking history, and number of years in the industry. A high prevalence of these symptoms was reported even though the degree of exposure to solvents and lubricants was within the current permissible exposure limits
The Infrared Properties of Hickson Compact Groups
Compact groups of galaxies provide a unique environment to study the
mechanisms by which star formation occurs amid continuous gravitational
encounters. We present 2MASS (JHK), Spitzer IRAC (3.5-8 micron) and MIPS (24
micron) observations of a sample of twelve Hickson Compact Groups (HCGs 2, 7,
16, 19, 22, 31, 42, 48, 59, 61, 62, and 90) that includes a total of 45
galaxies. The near-infrared colors of the sample galaxies are largely
consistent with being dominated by slightly reddened normal stellar
populations. Galaxies that have the most significant PAH and/or hot dust
emission (as inferred from excess 8 micron flux) also tend to have larger
amounts of extinction and/or K-band excess and stronger 24 micron emission, all
of which suggest ongoing star formation activity. We separate the twelve HCGs
in our sample into three types based on the ratio of the group HI mass to
dynamical mass. We find evidence that galaxies in the most gas-rich groups tend
to be the most actively star forming. Galaxies in the most gas-poor groups tend
to be tightly clustered around a narrow range in colors consistent with the
integrated light from a normal stellar population. We interpret these trends as
indicating that galaxies in gas-rich groups experience star formation and/or
nuclear actively until their neutral gas consumed, stripped, or ionized. The
galaxies in this sample exhibit a ``gap'' between gas-rich and gas-poor groups
in infrared color space that is sparsely populated and not seen in the Spitzer
First Look Survey sample. This gap may suggest a rapid evolution of galaxy
properties in response to dynamical effects. These results suggest that the
global properties of the groups and the local properties of the galaxies are
connected.Comment: 34 pages, 26 figures, accepted for publication in AJ, higher quality
images available in publicatio
Impacts of Muddy Bed Aggregates on Sediment Transport and Management in the tidal James River, VA
Aggregation state significantly influences the size, density and transport characteristics of fine sediment. Understanding sediment transport and deposition processes in the nationās navigable waterways is a primary mission for the US Army Corps of Engineers (USACE), particularly when it comes to infilling of navigation channels. In this study, a newly developed camera system was used to evaluate the aggregation state of eroded sediment from cores collected in the tidal James River, VA. Results showed that bed sediments were composed mostly of mud, but that erosion predominately occurred in the form of aggregates with median sizes 50-270x larger than the disaggregated sediment. Aggregate size weakly correlated to shear stress at levelsPa, as well as sand content and bed density. A numerical simulation demonstrated that mud aggregates were predicted to transport in incipient suspension or bedload, while disaggregated fines were predominately maintained in full suspension. This difference in transport mode has significant implication for channel infilling and sediment transport within the system
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