41,390 research outputs found
Experimental aspects of colour reconnection
This report summarises experimental aspects of the phenomena of colour
reconnection in W+W- production, concentrating on charged multiplicity and
event shapes, which were carried out as part of the Phenomenology Workshop on
LEP2 Physics, Oxford, Physics Department and Keble College, 14-18 April, 1997.
The work includes new estimates of the systematic uncertainty which may be
attributed to colour reconnection effects in experimental measurements of Mw.Comment: 10 pages, 4 figures. To be published in proceedings of Phenomenology
Workshop on LEP2 Physics, Oxford 14-18 April 199
Scientific publications of the bioscience programs division. Volume 5 - Planetary quarantine
Bibliography and indexes on planetary quarantin
The Determination of the `Diffusion Coefficients' and the Stellar Wind Velocities for X-Ray Binaries
The distribution of neutron stars (NS's) is determined by stationary solution
of the Fokker-Planck equation. In this work using the observed period changes
for four systems: Vela X-1, GX 301-2, Her X-1 and Cen X-3 we determined D, the
'diffusion coefficient',-parameter from the Fokker-Planck equation. Using
strong dependence of D on the velocity for Vela X-1 and GX 301-2, systems
accreting from a stellar wind, we determined the stellar wind velocity. For
different assumptions for a turbulent velocity we obtained . It is in good agreement with the stellar wind velocity determined by
other methods. We also determined the specific characteristic time scales for
the 'diffusion processes' in X-ray pulsars. It is of order of 200 sec for
wind-fed pulsars and 1000-10000 sec for the disk accreting systems.Comment: 8 pages, Latex, no figures, accepted for publication to Astronomical
and Astrophysical Transactions (1995). Admin note 20Feb2000: original
(broken) version now paper.tex.orig in source; fixed version with two bad
equations set in verbatim used for PS, paper.tex in sourc
Principal component analysis-based inversion of effective temperatures for late-type stars
We show how the range of application of the principal component
analysis-based inversion method of Paletou et al. (2015) can be extended to
late-type stars data. Besides being an extension of its original application
domain, for FGK stars, we also used synthetic spectra for our learning
database. We discuss our results on effective temperatures against previous
evaluations made available from Vizier and Simbad services at CDS.Comment: Accepted for publication in A&
A new method for the inversion of atmospheric parameters of A/Am stars
We present an automated procedure that derives simultaneously the effective
temperature , the surface gravity logg, the metallicity [Fe/H], and
the equatorial projected rotational velocity vsini for "normal" A and Am stars.
The procedure is based on the principal component analysis inversion method of
Paletou et al. (2015a). A sample of 322 high resolution spectra of F0-B9 stars,
retrieved from the Polarbase, SOPHIE, and ELODIE databases, were used to test
this technique with real data. We have selected the spectral region from
4400-5000\AA\ as it contains many metallic lines and the Balmer H line.
Using 3 datasets at resolving powers of R=42000, 65000 and 76000, about
6.6x synthetic spectra were calculated to build a large learning
database. The Online Power Iteration algorithm was applied to these learning
datasets to estimate the principal components (PC). The projection of spectra
onto the few PCs offered an efficient comparison metric in a low dimensional
space. The spectra of the well known A0- and A1-type stars, Vega and Sirius A,
were used as control spectra in the three databases. Spectra of other well
known A-type stars were also employed in order to characterize the accuracy of
the inversion technique. All observational spectra were inverted and
atmospheric parameters derived. After removal of a few outliers, the
PCA-inversion method appears to be very efficient in determining ,
[Fe/H], and vsini for A/Am stars. The derived parameters agree very well with
previous determinations. Using a statistical approach, deviations of around 150
K, 0.35 dex, 0.15 dex, and 2 km/s were found for , logg, [Fe/H], and
vsini with respect to literature values for A-type stars. The PCA-inversion
proves to be a very fast, practical, and reliable tool for estimating stellar
parameters of FGK and A stars, and deriving effective temperatures of M stars.Comment: 16 pages, 9 figures. Accepted in A&
Aspects of the confinement mechanism in Coulomb-gauge QCD
Phenomenological consequences of the infrared singular, instantaneous part of
the gluon propagator in Coulomb gauge are investigated. The corresponding quark
Dyson-Schwinger equation is solved, neglecting retardation and transverse
gluons and regulating the resulting infrared singularities. While the quark
propagator vanishes as the infrared regulator goes to zero, the frequency
integral over the quark propagator stays finite and well-defined. Solutions of
the homogeneous Bethe-Salpeter equation for the pseudoscalar and vector mesons
as well as for scalar and axial-vector diquarks are obtained. In the limit of a
vanishing infrared regulator the diquark masses diverge, while meson properties
and diquark radii remain finite and well-defined. These features are
interpreted with respect to the resulting aspects of confinement for colored
quark-quark correlations.Comment: 4 pages, 6 figure
An analysis of prop-fan/airframe aerodynamic integration
An approach to aerodynamic integration of turboprops and airframes, with emphasis placed upon wing mounted installations is addressed. Potential flow analytical techniques were employed to study aerodynamic integration of the prop fan propulsion concept with advanced, subsonic, commercial transport airframes. Three basic configurations were defined and analyzed: wing mounted prop fan at a cruise Mach number of 0.8, wing mounted prop fan in a low speed configuration, and aft mounted prop fan at a cruise Mach number of 0.8
Present state of knowledge of the upper atmosphere 1990: An assessment report
NASA is charged with the responsibility to report on the state of the knowledge of the Earth's upper atmosphere, particularly the stratosphere. Part 1 of this report, issued earlier this year, summarized the objectives, status, and accomplishments of the research tasks supported under NASA's Upper Atmosphere Research Program during the last two years. New findings since the last report to Congress was issued in 1988 are presented. Several scientific assessments of the current understanding of the chemical composition and physical structure of the stratosphere are included, in particular how the abundance and distribution of ozone is predicted to change in the future. These reviews include: a summary of the most recent international assessment of stratospheric ozone; a study of future chlorine and bromine loading of the atmosphere; a review of the photochemical and chemical kinetics data that are used as input parameters for the atmospheric models; a new assessment of the impact of Space Shuttle launches on the stratosphere; a summary of the environmental issues and needed research to evaluate the impact of the newly re-proposed fleet of stratospheric supersonic civil aircraft; and a list of the contributors to this report and the science assessments which have formed our present state of knowledge of the upper atmosphere and ozone depletion
Dissociating task difficulty from incongruence in face-voice emotion integration
In the everyday environment, affective information is conveyed by both the face and the voice. Studies have demonstrated that a concurrently presented voice can alter the way that an emotional face expression is perceived, and vice versa, leading to emotional conflict if the information in the two modalities is mismatched. Additionally, evidence suggests that incongruence of emotional valence activates cerebral networks involved in conflict monitoring and resolution. However, it is currently unclear whether this is due to task difficultyâthat incongruent stimuli are harder to categorizeâor simply to the detection of mismatching information in the two modalities. The aim of the present fMRI study was to examine the neurophysiological correlates of processing incongruent emotional information, independent of task difficulty. Subjects were scanned while judging the emotion of face-voice affective stimuli. Both the face and voice were parametrically morphed between anger and happiness and then paired in all audiovisual combinations, resulting in stimuli each defined by two separate values: the degree of incongruence between the face and voice, and the degree of clarity of the combined face-voice information. Due to the specific morphing procedure utilized, we hypothesized that the clarity value, rather than incongruence value, would better reflect task difficulty. Behavioral data revealed that participants integrated face and voice affective information, and that the clarity, as opposed to incongruence value correlated with categorization difficulty. Cerebrally, incongruence was more associated with activity in the superior temporal region, which emerged after task difficulty had been accounted for. Overall, our results suggest that activation in the superior temporal region in response to incongruent information cannot be explained simply by task difficulty, and may rather be due to detection of mismatching information between the two modalities
Indicator systems - resource use in organic systems
A balanced use of resources within organic farming systems is required to maintain sustainable systems. Hence, it is essential to have tools that can assess the use of resources within the farming system and their impact on the environment. The range of tools that have been developed include those assessing local farm-scale issues together with those that assess impacts at the global scale. At the global scale assessments are usually made on the basis of a unit of product whereas at the local scale assessments can also be made on an area basis. In addition, the tools also assess a variety of issues, e.g. biodiversity, pollution potential, energy and water use. The level of detail required for the different assessment tools differs substantially; nevertheless it is essential that the indicator systems developed are based on sound knowledge, are acceptable to the farmers and can guide their future actions
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