7,093 research outputs found
The Goldfish as a Model for Studying Neuroestrogen Synthesis, Localization, and Action in the Brain and Visual System
Organizational and activational effects of estrogen (E) in the central nervous system (CNS) are exerted directly by circulating E and indirectly after aromatization of circulating androgen to E in the brain itself. Understanding an environmental chemical's ability to disrupt E-dependent neural processes, therefore, requires attention to both pathways. Because aromatase (Aro) is highly expressed in teleost brain, when compared to mammals and other vertebrates, fish are technically advantageous for localization and regulation studies and may also provide a model in which the functional consequences of brain-derived (neuro-)E synthesis are exaggerated. Recently, Aro was immunolocalized in cell bodies and fiber projections of second- and third-order neurons of the goldfish retina and in central visual processing areas. Authentic Aro enzyme activity was verified biochemically, suggesting a heretofore unrecognized role of sex steroids in the visual system. Initial studies show that in vivo treatment with aromatizable androgen or E increases calmodulin synthesis and calmodulin protein in retina and also affects retinal protein and DNA. Whether there are related changes in the processing of visual information that is essential for seasonal reproduction or in the generative and regenerative capacity of the goldfish visual system requires further investigation. IMAGES.National Science Foundation (DCB8916809
Mg I emission lines at 12 and 18 micrometer in K giants
The solar Mg I emission lines at 12 micrometer have already been observed and
analyzed well. Previous modeling attempts for other stars have, however, been
made only for Procyon and two cool evolved stars, with unsatisfactory results
for the latter. We present high-resolution observational spectra for the K
giants Pollux, Arcturus, and Aldebaran, which show strong Mg I emission lines
at 12 micrometer as compared to the Sun. We also present the first observed
stellar emission lines from Mg I at 18 micrometer and from Al I, Si I, and
presumably Ca I at 12 micrometer. To produce synthetic line spectra, we employ
standard non-LTE modeling for trace elements in cool stellar photospheres. We
compute model atmospheres with the MARCS code, apply a comprehensive magnesium
model atom, and use the radiative transfer code MULTI to solve for the
magnesium occupation numbers in statistical equilibrium. We successfully
reproduce the observed Mg I emission lines simultaneously in the giants and in
the Sun, but show how the computed line profiles depend critically on atomic
input data and how the inclusion of energy levels with n > 9 and collisions
with neutral hydrogen are necessary to obtain reasonable fits.Comment: 9 pages, 6 figures, accepted for publication in Astronomy &
Astrophysic
F.A.R.M. Phase One
Non-Peer ReviewedF.A.R.M. Phase one is a computer program which controls the processing of soil samples at Plains Innovative Laboratory Services in Saskatoon. This video describes the four steps of the soil testing process and shows how this computer program maintains control of the sample flow through the laboratory and maintains the integrity of the data in the system. The video follows the soil samples through the various analytical procedures up to the printing of the final report which is faxed and mailed to the fertilizer dealer or farmer. The showing of this video will demonstrate the procedures involved in the analysis of a soil sample and outline the quality assurance procedures that are part of the system
Candidate Tidal Dwarf Galaxies in the Compact Group CG J1720-67.8
This is the second part of a detailed study of the ultracompact group CG
J1720-67.8: in the first part we have focused the attention on the three main
galaxies of the group and we have identified a number of candidate tidal dwarf
galaxies (TDGs). Here we concentrate on these candidate TDGs. Absolute
photometry of these objects in BVRJHKs bands confirms their relatively blue
colors, as we already expected from the inspection of optical and near-infrared
color maps and from the presence of emission-lines in the optical spectra. The
physical conditions in such candidate TDGs are investigated through the
application of photoionization models, while the optical colors are compared
with grids of spectrophotometric evolutionary synthesis models from the
literature. Although from our data self-gravitation cannot be proved for these
objects, their general properties are consistent with those of other TDG
candidates. Additionally we present the photometry of a few ``knots'' detected
in the immediate surroundings of CG J1720-67.8 and consider the possibility
that these objects might belong to a dwarf population associated with the
compact group.Comment: Accepted for publication in the Astrophysical Journa
Benzyl 5-hydroxy-4-oxapentacyclo[5.4.1.02,6.03,10.08,11]dodecane-3-carboxylate
The title compound, C19H18O4, exhibits a long C—C bond [1.575 (2) Å] in the cage structure. In the crystal, pairs of O—H⋯O hydrogen bonds link the molecules into centrosymmetric dimers. C—H⋯O interactions also occur
8-(Biphenyl-4-yl)-8-hydroxypentacyclo[5.4.0.02,6.03,10.05,9]undecan-11-one ethylene ketal
The title compound, C25H24O3, synthesized as a potential chiral catalyst, exhibits a range of C—C bond lengths in the pentacycloundecane cage between 1.5144 (18) and 1.5856 (16) Å. The two benzene rings are not planar with respect to each other, but rather are twisted at a torsion angle of 34.67 (17)°. The molecule has an intramolecular O—H⋯O interaction and participates in two C—H⋯O intermolecular interactions to form a one-dimensional chain
The NASA/GSFC hydrogen maser program: A review of recent data
Data is presented on the phase and frequency stability, over time periods extending to one week, of the new NR field operable hydrogen masers developed by the Applied Physics Laboratory (APL) and the older NX and NP field operable hydrogen masers developed by Goddard Space Flight Center and maintained and upgraded by Bendix Field Engineering Corporation (BFEC). Data is presented on the NR masers in the laboratory showing frequency stabilities well into the 10 to the -15th power range and phase stabilities well into the 100 ps range for periods of up to one day. Data is presented on upgraded NP masers in the laboratory showing that the frequency stability has been improved substantially to virtually the NR level. VLBI data is presented on the phase difference between NX-2 at Owens Valley, California and NR-2 at Fort Davis, Texas for a one week period showing, after removal of a constant frequency drift, a 350 ps RMS phase stability
Fourth-generation SM imprints in B -> K^*l^+l^- decays with polarized K^*
The implication of the fourth-generation quarks in the B -> K^*l^+l^-
(l=mu,tau) decays, when K^* meson is longitudinally or transversely polarized,
is presented. In this context, the dependence of the branching ratio with
polarized K^* and the helicity fractions (f_{L,T}) of K^* meson are studied. It
is observed that the polarized branching ratios as well as helicity fractions
are sensitive to the NP parameters, especially when the final state leptons are
tauons. Hence the measurements of these observables at LHC can serve as a good
tool to investigate the indirect searches of new physics beyond the Standard
Model.Comment: 13 pages, 10 figures, V2: some of the graphs are modified according
to the new data from recent experiments. arXiv admin note: substantial text
overlap with arXiv:1107.569
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