3,312 research outputs found
Changes in vegetation spectra with deterioration of leaves under two methods of preservation
An experiment to measure changes in leaf spectra under different methods of preservation over time was conducted. The spectral measurements were made by a three band hand held radiometer which simulated three Thematic Mapper (TM) bands: TM3, TM4, and TM5. Daily spectral measurements of white oak leaves under three preservation treatments were made. The spectral readings over three treatments (fresh, bottled, and bagged vegetation) were indistinguishable in bands TM3 and TM5 for up to 4 days after collection. After that time bagged and bottled samples showed significant increases in reflected energy caused by loss of chlorophyll from and dehydration of the vegetation. No significant variation in the reflectance values from TM4 over preservation type for the experimental period was observed
Hyperatlas: A New Framework for Image Federation
Hyperatlas is an open standard intended to facilitate the large-scale
federation of image-based data. The subject of hyperatlas is the space of
sphere-to-plane projection mappings (the FITS-WCS information), and the
standard consists of coherent collections of these on which data can be
resampled and thereby federated with other image data. We hope for a
distributed effort that will produce a multi-faceted image atlas of the sky,
made by federating many different surveys at different wavelengths and
different times. We expect that hyperatlas-compliant imagery will be published
and discovered through an International Virtual Observatory Alliance (IVOA)
registry, and that grid-based services will emerge for the required resampling
and mosaicking.Comment: Published in ADASS XIII proceeding
Atlasmaker: A Grid-based Implementation of the Hyperatlas
The Atlasmaker project is using Grid technology, in combination with NVO
interoperability, to create new knowledge resources in astronomy. The product
is a multi-faceted, multi-dimensional, scientifically trusted image atlas of
the sky, made by federating many different surveys at different wavelengths,
times, resolutions, polarizations, etc. The Atlasmaker software does resampling
and mosaicking of image collections, and is well-suited to operate with the
Hyperatlas standard. Requests can be satisfied via on-demand computations or by
accessing a data cache. Computed data is stored in a distributed virtual file
system, such as the Storage Resource Broker (SRB). We expect these atlases to
be a new and powerful paradigm for knowledge extraction in astronomy, as well
as a magnificent way to build educational resources. The system is being
incorporated into the data analysis pipeline of the Palomar-Quest synoptic
survey, and is being used to generate all-sky atlases from the 2MASS, SDSS, and
DPOSS surveys for joint object detection.Comment: Published in the Proceedings of ADASS XI
A Discrete Four Stroke Quantum Heat Engine Exploring the Origin of Friction
The optimal power performance of a first principle quantum heat engine model
shows friction-like phenomena when the internal fluid Hamiltonian does not
commute with the external control field. The model is based on interacting
two-level-systems where the external magnetic field serves as a control
variable.Comment: 4 pages 3 figure
Mirror matter admixtures in K_L \to \gamma\gamma
Based on possible albeit tiny, admixtures of mirror matter in ordinary mesons
we study the K_L \to \gamma\gamma transition. We find that this process can be
described with a small SU(3) symmetry breaking of only 3%. We also determine
the eta-eta' mixing angle and the pseudoscalar decay constants. The results for
these parameters are consistent with some obtained in the literature. They
favor two recent determinations; one based on two analytical constraints, and
another one based on next-to-leading order power corrections
The decay pi0 to gamma gamma to next to leading order in Chiral Perturbation Theory
The two photon decay width of the neutral pion is analyzed within the
combined framework of Chiral Perturbation Theory and the 1/Nc expansion up to
order p^6 and p^4 times 1/Nc in the decay amplitude. The eta' is explicitly
included in the analysis. It is found that the decay width is enhanced by about
4.5% due to the isospin-breaking induced mixing of the pure U(3) states. This
effect, which is of leading order in the low energy expansion, is shown to
persist nearly unchanged at next to leading order. The chief prediction for the
width with its estimated uncertainty is 8.10+-0.08 eV. This prediction at the
1% level makes the upcomming precision measurement of the decay width even more
urgent.
Observations on the eta and eta' can also be made, especially about their
mixing, which is shown to be significantly affected by next to leading order
corrections.Comment: 21 pages, two figure
Pseudoscalar Meson Mixing in Effective Field Theory
We show that for any effective field theory of colorless meson fields, the
mixing schemes of particle states and decay constants are not only related but
also determined exclusively by the kinetic and mass Lagrangian densities. In
the general case, these are bilinear in terms of the intrinsic fields and
involve non-diagonal kinetic and mass matrices. By applying three consecutive
steps this Lagrangian can be reduced into the standard quadratic form in terms
of the physical fields. These steps are : (i) the diagonalization of the
kinetic matrix, (ii) rescaling of the fields, and (iii) the diagonalization of
the mass matrix. In case, where the dimensions of the non-diagonal kinetic and
mass sub-matrices are respectively, and , this procedure
leads to mixing schemes which involve angles and
field rescaling parameters. This observation holds true irrespective with the
type of particle interactions presumed. The commonly used mixing schemes,
correspond to a proper choice of the kinetic and mass matrices, and are derived
as special cases. In particular, - mixing, requires one angle, if
and only if, the kinetic term with the intrinsic fields has a quadratic form.Comment: REVTeX, 6 page
Mycorrhizal situation of native trees in the Brazilian tropical ecosystems Varzea, Igapo, Terra firme and Cerrados.
Quark structure of pseudoscalar mesons
I review to which extent the properties of pseudoscalar mesons can be
understood in terms of the underlying quark (and eventually gluon) structure.
Special emphasis is put on the progress in our understanding of eta-eta'
mixing. Process-independent mixing parameters are defined, and relations
between different bases and conventions are studied. Both, the low-energy
description in the framework of Chiral Perturbation Theory and the high-energy
application in terms of light-cone wave functions for partonic Fock states, are
considered. A thorough discussion of theoretical and phenomenological
consequences of the mixing approach will be given. Finally, I will discuss
mixing with other states pi^0, eta(c), ...).Comment: 48 pages, 7 figures, using epsfig.st
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