17,788 research outputs found
Ion-scale spectral break of solar wind turbulence at high and low beta
The power spectrum of magnetic fluctuations in the solar wind at 1 AU displays a break between two power laws in the range of spacecraft-frame frequencies 0.1 to 1 Hz. These frequencies correspond to spatial scales in the plasma frame near the proton gyroradius ρi and proton inertial length di. At 1 AU it is difficult to determine which of these is associated with the break, since [Formula: see text] and the perpendicular ion plasma beta is typically β⊥i∼1. To address this, several exceptional intervals with β⊥i≪1 and β⊥i≫1 were investigated, during which these scales were well separated. It was found that for β⊥i≪1 the break occurs at di and for β⊥i≫1 at ρi, i.e., the larger of the two scales. Possible explanations for these results are discussed, including Alfvén wave dispersion, damping, and current sheets
THREE-DIMENSIONAL STRUCTURE OF SOLAR WIND TURBULENCE
We present a measurement of the scale-dependent, three-dimensional structure of the magnetic field fluctuations in inertial range solar wind turbulence with respect to a local, physically motivated coordinate system. The Alfvenic fluctuations are three-dimensionally anisotropic, with the sense of this anisotropy varying from large to small scales. At the outer scale, the magnetic field correlations are longest in the local fluctuation direction, consistent with Alfven waves. At the proton gyroscale, they are longest along the local mean field direction and shortest in the direction perpendicular to the local mean field and the local field fluctuation. The compressive fluctuations are highly elongated along the local mean field direction, although axially symmetric perpendicular to it. Their large anisotropy may explain why they are not heavily damped in the solar wind
Personalization framework for adaptive robotic feeding assistance
The final publication is available at link.springer.comThe deployment of robots at home must involve robots with pre-defined skills and the capability of
personalizing their behavior by non-expert users. A framework to tackle this personalization is presented and applied
to an automatic feeding task. The personalization involves the caregiver providing several examples of feeding using
Learning-by- Demostration, and a ProMP formalism to compute an overall trajectory and the variance along the path.
Experiments show the validity of the approach in generating different feeding motions to adapt to user’s preferences,
automatically extracting the relevant task parameters. The importance of the nature of the demonstrations is also
assessed, and two training strategies are compared. © Springer International Publishing AG 2016.Peer ReviewedPostprint (author's final draft
Epidemiological characteristics of Pandemic Influenza A (H1N1-2009) in Zhanjiang, China
Background: A novel influenza A virus strain (H1N1-2009) spread first in Mexico and the United Stated in late April 2009, leading to the first influenza pandemic of the 21st century. The objective of this study was to determine the epidemiological and virological characteristics of the pandemic influenza A (H1N1-2009) in Zhanjiang, China. Methods: The case and outbreak reports of influenza-like illness (ILI) were collected from the Chinese information system of disease control and prevention and the influenza surveillance system of Zhanjiang city. Real-time RT-PCR was conducted, and epidemic and virological characteristics of the virus were analyzed using descriptive epidemiological methods and Chi-square trend tests. Results: A total of 276 reported cases were confirmed from July 16, 2009 to June 30, 2010. The attack rate of outbreak was from 1.1% to 6.0%. The disease peak occurred in December 2009, after which the outbreak subsided gradually. The last case was confirmed in April 2010. Conclusion: The main population struck by the H1N1-2009 virus was young adults, youths and children. The outbreaks most frequently occurred in schools, and most cases were acquired locally
Multimode metal-lined capillaries for Raman collection and sensing
Reflective metal-lined capillary waveguides are useful for laser-power delivery or for collecting scattered light in sensing applications. We theoretically examine the multimode propagation of polarized light in largediameter, metallized, capillary waveguides using a new perturbation technique valid for all waveguide modes. This modeling permits prediction of the collection efficiency of Raman or fluorescent light produced in the waveguide at all angles. These theoretical results are supported by measuring the intensity and angular distribution of collected scattered gas-Raman Stokes power. © 2010 Optical Society of America
sscMap: An extensible Java application for connecting small-molecule drugs using gene-expression signatures
Background: Connectivity mapping is a process to recognize novel
pharmacological and toxicological properties in small molecules by comparing
their gene expression signatures with others in a database. A simple and robust
method for connectivity mapping with increased specificity and sensitivity was
recently developed, and its utility demonstrated using experimentally derived
gene signatures.
Results: This paper introduces sscMap (statistically significant connections'
map), a Java application designed to undertake connectivity mapping tasks using
the recently published method. The software is bundled with a default
collection of reference gene-expression profiles based on the publicly
available dataset from the Broad Institute Connectivity Map 02, which includes
data from over 7000 Affymetrix microarrays, for over 1000 small-molecule
compounds, and 6100 treatment instances in 5 human cell lines. In addition, the
application allows users to add their custom collections of reference profiles
and is applicable to a wide range of other 'omics technologies.
Conclusions: The utility of sscMap is two fold. First, it serves to make
statistically significant connections between a user-supplied gene signature
and the 6100 core reference profiles based on the Broad Institute expanded
dataset. Second, it allows users to apply the same improved method to
custom-built reference profiles which can be added to the database for future
referencing. The software can be freely downloaded from
http://purl.oclc.org/NET/sscMapComment: 3 pages, 1 table, 1 eps figur
Identifying Boosted Objects with N-subjettiness
We introduce a new jet shape -- N-subjettiness -- designed to identify
boosted hadronically-decaying objects like electroweak bosons and top quarks.
Combined with a jet invariant mass cut, N-subjettiness is an effective
discriminating variable for tagging boosted objects and rejecting the
background of QCD jets with large invariant mass. In efficiency studies of
boosted W bosons and top quarks, we find tagging efficiencies of 30% are
achievable with fake rates of 1%. We also consider the discovery potential for
new heavy resonances that decay to pairs of boosted objects, and find
significant improvements are possible using N-subjettiness. In this way,
N-subjettiness combines the advantages of jet shapes with the discriminating
power seen in previous jet substructure algorithms.Comment: 26 pages, 26 figures, 2 tables; v2: references added; v3: discussion
of results extende
Line versus Flux Statistics -- Considerations for the Low Redshift Lyman-alpha Forest
The flux/transmission power spectrum has become a popular statistical tool in
studies of the high redshift () Lyman-alpha forest. At low redshifts,
where the forest has thinned out into a series of well-isolated absorption
lines, the motivation for flux statistics is less obvious. Here, we study the
relative merits of flux versus line correlations, and derive a simple condition
under which one is favored over the other on purely statistical grounds.
Systematic errors probably play an important role in this discussion, and they
are outlined as well.Comment: 6 pages, to appear in "The IGM/Galaxy Connection: The Distribution of
Baryons at z=0", eds. J. L. Rosenberg and M. E. Putma
Agricultural origins and the isotopic identity of domestication in northern China
Stable isotope biochemistry (δ 13C and δ 15N) and radiocarbon dating of ancient human and animal bone document 2 distinct phases of plant and animal domestication at the Dadiwan site in northwest China. The first was brief and nonintensive: at various times between 7900 and 7200 calendar years before present (calBP) people harvested and stored enough broomcorn millet (Panicum miliaceum) to provision themselves and their hunting dogs (Canis sp.) throughout the year. The second, much more intensive phase was in place by 5900 calBP: during this time both broomcorn and foxtail (Setaria viridis spp. italica) millets were cultivated and made significant contributions to the diets of people, dogs, and pigs (Sus sp.). The systems represented in both phases developed elsewhere: the earlier, low-intensity domestic relationship emerged with hunter-gatherers in the arid north, while the more intensive, later one evolved further east and arrived at Dadiwan with the Yangshao Neolithic. The stable isotope methodology used here is probably the best means of detecting the symbiotic human-plantanimal linkages that develop during the very earliest phases of domestication and is thus applicable to the areas where these connections first emerged and are critical to explaining how and why agriculture began in East Asia
Naive bayes classification of uncertain data
Traditional machine learning algorithms assume that data are exact or precise. However, this assumption may not hold in some situations because of data uncertainty arising from measurement errors, data staleness, and repeated measurements, etc. With uncertainty, the value of each data item is represented by a probability distribution function (pdf). In this paper, we propose a novel naive Bayes classification algorithm for uncertain data with a pdf. Our key solution is to extend the class conditional probability estimation in the Bayes model to handle pdf's. Extensive experiments on UCI datasets show that the accuracy of naive Bayes model can be improved by taking into account the uncertainty information. © 2009 IEEE.published_or_final_versionThe 9th IEEE International Conference on Data Mining (ICDM), Miami, FL., 6-9 December 2009. In Proceedings of the 9th ICDM, 2009, p. 944-94
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