7,298 research outputs found
A New Technique for Heterodyne Spectroscopy: Least-Squares Frequency Switching (LSFS)
We describe a new technique for heterodyne spectroscopy, which we call
Least-Squares Frequency Switching, or LSFS. This technique avoids the need for
a traditional reference spectrum, which--when combined with the on-source
spectrum--introduces both noise and systematic artifacts such as ``baseline
wiggles''. In contrast, LSFS derives the spectrum directly, and in addition the
instrumental gain profile. The resulting spectrum retains nearly the full
theoretical sensitivity and introduces no systematic artifacts.
Here we discuss mathematical details of the technique and use numerical
experiments to explore optimum observing schemas. We outline a modification
suitable for computationally difficult cases as the number of spectral channels
grows beyond several thousand. We illustrate the method with three real-life
examples. In one of practical interest, we created a large contiguous bandwidth
aligning three smaller bandwidths end-to-end; radio astronomers are often faced
with the need for a larger contiguous bandwidth than is provided with the
available correlator.Comment: 37 pages, 8 figure
Arkansas Pteridophyte Flora Update: A New Checklist and Additional County-level Occurrence Records
An Explicit SU(12) Family and Flavor Unification Model
An explicit SUSY SU(12) unification model with three light chiral families is
presented which avoids any external flavor symmetries. The hierarchy of quark
and lepton masses and mixings is explained by higher dimensional Yukawa
interactions involving Higgs bosons containing SU(5) singlet fields with VEVs
appearing at or below the SUSY GUT scale of 2 \times 10^{16} GeV, approximately
50 times smaller than the SU(12) unification scale. The model has been found to
be in good agreement with the observed quark and lepton masses and mixings,
with nearly all prefactors of O(1) in the four Dirac and one Majorana fermion
mass matrices.Comment: 7 pages, in proceedings of the CETUP*2012 Workshop, Lead, SD, 10 July
- 1 August 201
Checklist and Distribution of Arkansas Pteridophytes
Over the past 14 years, an effort was made to summarize and improve our knowledge of the Arkansas pteridophyte flora beyond that developed by Taylor and Demaree (1979). They presented a flora of 68 species plus 2 varieties plus 4 hybrids, for a total of 74 taxa vouchered with 1335 county-level occurrence records. Changes in accepted nomenclature, field work, and herbaria searches have added as new to the flora 10 species plus 1 variety plus 7 hybrids, supported with 74 county-level occurrence records. Another 815 county-level occurrence records were added to the known flora. The Arkansas pteridophyte flora now consists of 78 species plus 3 varieties plus 11hybrids, supported with 2224 county-level occurrence records. Achecklist, 92 distribution maps, a history of Arkansas pteridophyte floristics, corrective nomenclatural notes, and a phylogeny based ona recent national treatment on pteridophytes are provided
Euclidean random matrix theory: low-frequency non-analyticities and Rayleigh scattering
By calculating all terms of the high-density expansion of the euclidean
random matrix theory (up to second-order in the inverse density) for the
vibrational spectrum of a topologically disordered system we show that the
low-frequency behavior of the self energy is given by and not , as claimed previously.
This implies the presence of Rayleigh scattering and long-time tails of the
velocity autocorrelation function of the analogous diffusion problem of the
form .Comment: 27 page
Resveratrol given intraperitoneally does not inhibit the growth of high-risk t(4;11) acute lymphoblastic leukemia cells in a NOD/SCID mouse model.
The efficacy of resveratrol as a preventive agent against the growth of t(4;11) acute lymphoblastic leukemia (ALL) was evaluated in NOD.CB17-Prkdcscid/J mice engrafted with the human t(4;11) ALL SEM cell line. SEM cells were injected into the tail vein and engraftment was monitored by flow cytometry. Once engraftment was observed, mice were injected intraperitoneally with resveratrol (10 mg/kg body weight) dissolved in dimethylsulfoxide (DMSO) or DMSO alone (control) every other day, or vincristine (0.5 mg/kg body weight) 3 times per week for 4 weeks (n=16 per group). Comparisons of the percent of human leukemia cells in blood and survival curves showed resveratrol did not inhibit progression of the disease. Liquid chromatography-tandem mass spectrometry analyses of mouse sera showed resveratrol was rapidly metabolized to glucuronidated and sulfated forms 1 h post-injection, with low to no resveratrol or metabolites observed in sera by 24-48 h. These data indicate that in contrast to findings in in vitro models, parenterally administered resveratrol does not have potential as a preventive agent against high risk t(4;11) ALL
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