1,981 research outputs found
Kaon mixing matrix elements from beyond-the-Standard-Model operators in staggered chiral perturbation theory
Models of new physics induce K-Kbar mixing operators having Dirac structures
other than the "left-left" form of the Standard Model. We calculate the
functional form of the corresponding B-parameters at next-to-leading order in
both SU(3) and SU(2) staggered chiral perturbation theory (SChPT). Numerical
results for these matrix elements are being generated using improved staggered
fermions; our results can be used to extrapolate these matrix elements to the
physical light and strange quark masses. The SU(3) SChPT results turn out to be
much simpler than that for the Standard Model B_K operator, due to the absence
of chiral suppression in the new operators. The SU(2) SChPT result is of
similar simplicity to that for B_K. In fact, in the latter case, the chiral
logarithms for two of the new B-parameters are identical to those for B_K,
while those for the other two new B-parameters are of opposite sign. In
addition to providing results for the 2+1 flavor theory in SU(3) SChPT and the
1+1+1 flavor theory in SU(2) SChPT, we present the corresponding continuum
partially quenched results, as these are not available in the literature.Comment: 16 pages, 3 figures. Typos corrected--published versio
Melatonin Alters Age-Related Changes in Transcription Factors and Kinase Activation
Male mice were fed 40 ppm melatonin for 2 months prior to sacrifice at age 26 months, and compared with both 26 and 4 month-old untreated controls. The nuclear translocation of NF-κB increased with age in both brain and spleen and this was reversed by melatonin only in brain. Another transcription factor, AP-1 was increased with age in the spleen and not in brain and this could be blocked by melatonin treatment. The fraction of the active relative to the inactive form of several enabling kinases was compared. The proportion of activated ERK was elevated with age in brain and spleen but this change was unresponsive to melatonin. A similar age-related increase in glial fibrillary acidic protein (GFAP) was also refractory to melatonin treatment. The cerebral melatonin M1 receptor decreased with age in brain but increased in spleen. The potentially beneficial nature of melatonin for the preservation of brain function with aging was suggested by the finding that an age-related decline in cortical synaptophysin levels was prevented by dietary melatonin
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Management of pediatric uveitis
Pediatric uveitis is a topic of special interest not only because of the unique diagnostic and therapeutic challenges but also because of the lifetime burden of vision loss if the problem is not adequately treated, as well as the economic and psychological toll on the family. Often, uveitis in children is discovered as part of a routine eye exam; this silent, insidious inflammation can be difficult to treat and can lead to further complications if not handled skillfully. Corticosteroids have long been the mainstay of therapy; however, the significant associated side effects mandate a corticosteroid-sparing therapeutic regimen in pursuit of remission. In this review, we cover the therapeutic options for pediatric uveitis, specifically focusing on the most common non-infectious varieties, juvenile idiopathic arthritis-associated uveitis and pars planitis
Principal Component Analysis with Noisy and/or Missing Data
We present a method for performing Principal Component Analysis (PCA) on
noisy datasets with missing values. Estimates of the measurement error are used
to weight the input data such that compared to classic PCA, the resulting
eigenvectors are more sensitive to the true underlying signal variations rather
than being pulled by heteroskedastic measurement noise. Missing data is simply
the limiting case of weight=0. The underlying algorithm is a noise weighted
Expectation Maximization (EM) PCA, which has additional benefits of
implementation speed and flexibility for smoothing eigenvectors to reduce the
noise contribution. We present applications of this method on simulated data
and QSO spectra from the Sloan Digital Sky Survey.Comment: Accepted for publication in PASP; v2 with minor updates, mostly to
bibliograph
Magellan/M2FS Spectroscopy of Galaxy Clusters: Stellar Population Model and Application to Abell 267
We report the results of a pilot program to use the Magellan/M2FS
spectrograph to survey the galactic populations and internal kinematics of
galaxy clusters. For this initial study, we present spectroscopic measurements
for quiescent galaxies observed along the line of sight to the galaxy
cluster Abell 267 (). We develop a Bayesian method for modeling the
integrated light from each galaxy as a simple stellar population, with free
parameters that specify redshift () and characteristic age,
metallicity (), alpha-abundance (), and
internal velocity dispersion () for individual galaxies.
Parameter estimates derived from our 1.5-hour observation of A267 have median
random errors of ,
, $\sigma_{\mathrm{[Fe/H]}}=0.11\
\mathrm{dex}\sigma_{[\alpha/\mathrm{Fe}]}=0.07\ \mathrm{dex}\sigma_{\sigma_\mathrm{int}}=20\ \mathrm{km\ s^{-1}}$. In a companion paper,
we use these results to model the structure and internal kinematics of A267.Comment: 16 pages, 11 figures, accepted for publication in The Astronomical
Journa
TB88: Descriptive and Comparative Studies of Maine Lakes
This is a descriptive and comparative study of 17 lakes in Maine. The major objectives of this study are (1) to characterize the pelagial zone of the lakes physically, chemically, and biologically, (2) to assess bacterial pollution, (3) to compare the lakes to each other and classify them trophically, and (4) to compare the lakes to others in different geographic regions.https://digitalcommons.library.umaine.edu/aes_techbulletin/1117/thumbnail.jp
AGB Sodium Abundances in the Globular Cluster 47 Tucanae (NGC 104)
A recent analysis comparing the [Na/Fe] distributions of red giant branch
(RGB) and asymptotic giant branch (AGB) stars in the Galactic globular cluster
NGC 6752 found that the ratio of Na-poor to Na-rich stars changes from 30:70 on
the RGB to 100:0 on the AGB. The surprising paucity of Na-rich stars on the AGB
in NGC 6752 warrants additional investigations to determine if the failure of a
significant fraction of stars to ascend the AGB is an attribute common to all
globular clusters. Therefore, we present radial velocities, [Fe/H], and [Na/Fe]
abundances for 35 AGB stars in the Galactic globular cluster 47 Tucanae (47
Tuc; NGC 104), and compare the AGB [Na/Fe] distribution with a similar RGB
sample published previously. The abundances and velocities were derived from
high resolution spectra obtained with the Michigan/Magellan Fiber System (M2FS)
and MSpec spectrograph on the Magellan-Clay 6.5m telescope. We find the average
heliocentric radial velocity and [Fe/H] values to be =-18.56 km s^-1
(sigma=10.21 km s^-1) and =-0.68 (sigma=0.08), respectively, in
agreement with previous literature estimates. The average [Na/Fe] abundance is
0.12 dex lower in the 47 Tuc AGB sample compared to the RGB sample, and the
ratio of Na-poor to Na-rich stars is 63:37 on the AGB and 45:55 on the RGB.
However, in contrast to NGC 6752, the two 47 Tuc populations have nearly
identical [Na/Fe] dispersion and interquartile range values. The data presented
here suggest that only a small fraction <20% of Na-rich stars in 47 Tuc may
fail to ascend the AGB. Regardless of the cause for the lower average [Na/Fe]
abundance in AGB stars, we find that Na-poor stars and at least some Na-rich
stars in 47 Tuc evolve through the early AGB phase. [abridged]Comment: Accepted for publication in the Astronomical Journal; 15 pages; 8
figures; 4 table
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