1,411 research outputs found
Skeletal Muscle PGC-1β Signaling is Sufficient to Drive an Endurance Exercise Phenotype and to Counteract Components of Detraining in Mice
Peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α and -1β serve as master transcriptional regulators of muscle mitochondrial functional capacity and are capable of enhancing muscle endurance when overexpressed in mice. We sought to determine whether muscle-specific transgenic overexpression of PGC-1β affects the detraining response following endurance training. First, we established and validated a mouse exercise-training-detraining protocol. Second, using multiple physiological and gene expression end points, we found that PGC-1β overexpression in skeletal muscle of sedentary mice fully recapitulated the training response. Lastly, PGC-1β overexpression during the detraining period resulted in partial prevention of the detraining response. Specifically, an increase in the plateau at which O2 uptake (V̇o2) did not change from baseline with increasing treadmill speed [peak V̇o2 (ΔV̇o2max)] was maintained in trained mice with PGC-1β overexpression in muscle 6 wk after cessation of training. However, other detraining responses, including changes in running performance and in situ half relaxation time (a measure of contractility), were not affected by PGC-1β overexpression. We conclude that while activation of muscle PGC-1β is sufficient to drive the complete endurance phenotype in sedentary mice, it only partially prevents the detraining response following exercise training, suggesting that the process of endurance detraining involves mechanisms beyond the reversal of muscle autonomous mechanisms involved in endurance fitness. In addition, the protocol described here should be useful for assessing early-stage proof-of-concept interventions in preclinical models of muscle disuse atrophy
Further results on entanglement detection and quantification from the correlation matrix criterion
The correlation matrix (CM) criterion is a recently derived powerful
sufficient condition for the presence of entanglement in bipartite quantum
states of arbitrary dimensions. It has been shown that it can be stronger than
the positive partial transpose (PPT) criterion, as well as the computable cross
norm or realignment (CCNR) criterion in different situations. However, it
remained as an open question whether there existed sets of states for which the
CM criterion could be stronger than both criteria simultaneously. Here, we give
an affirmative answer to this question by providing examples of entangled
states that scape detection by both the PPT and CCNR criteria whose
entanglement is revealed by the CM condition. We also show that the CM can be
used to measure the entanglement of pure states and obtain lower bounds for the
entanglement measure known as tangle for general (mixed) states.Comment: 13 pages, no figures; added references, minor changes; section 4.3
added, to appear in J. Phys.
The cosmological origin of the Tully-Fisher relation
We use high-resolution cosmological simulations that include the effects of
gasdynamics and star formation to investigate the origin of the Tully-Fisher
relation in the standard Cold Dark Matter cosmogony. Luminosities are computed
for each model galaxy using their full star formation histories and the latest
spectrophotometric models. We find that at z=0 the stellar mass of model
galaxies is proportional to the total baryonic mass within the virial radius of
their surrounding halos. Circular velocity then correlates tightly with the
total luminosity of the galaxy, reflecting the equivalence between mass and
circular velocity of systems identified in a cosmological context. The slope of
the relation steepens slightly from the red to the blue bandpasses, and is in
fairly good agreement with observations. Its scatter is small, decreasing from
\~0.45 mag in the U-band to ~0.34 mag in the K-band. The particular
cosmological model we explore here seems unable to account for the zero-point
of the correlation. Model galaxies are too faint at z=0 (by about two
magnitudes) if the circular velocity at the edge of the luminous galaxy is used
as an estimator of the rotation speed. The Tully-Fisher relation is brighter in
the past, by about ~0.7 magnitudes in the B-band at z=1, at odds with recent
observations of z~1 galaxies. We conclude that the slope and tightness of the
Tully-Fisher relation can be naturally explained in hierarchical models but
that its normalization and evolution depend strongly on the star formation
algorithm chosen and on the cosmological parameters that determine the
universal baryon fraction and the time of assembly of galaxies of different
mass.Comment: 5 pages, 4 figures included, submitted to ApJ (Letters
Produção de forragem de genótipos de sorgo silageiro em diferentes ambientes.
O presente trabalho tem como objetivo avaliar o comportamento de 22 híbridos experimentais de sorgo silageiro em seis ambientes
Density Variations in the NW Star Stream of M31
The Pan Andromeda Archeological Survey (PAndAS) CFHT Megaprime survey of the
M31-M33 system has found a star stream which extends about 120 kpc NW from the
center of M31. The great length of the stream, and the likelihood that it does
not significantly intersect the disk of M31, means that it is unusually well
suited for a measurement of stream gaps and clumps along its length as a test
for the predicted thousands of dark matter sub-halos. The main result of this
paper is that the density of the stream varies between zero and about three
times the mean along its length on scales of 2 to 20 kpc. The probability that
the variations are random fluctuations in the star density is less than 10^-5.
As a control sample we search for density variations at precisely the same
location in stars with metallicity higher than the stream, [Fe/H]=[0, -0.5] and
find no variations above the expected shot noise. The lumpiness of the stream
is not compatible with a low mass star stream in a smooth galactic potential,
nor is it readily compatible with the disturbance caused by the visible M31
satellite galaxies. The stream's density variations appear to be consistent
with the effects of a large population of steep mass function dark matter
sub-halos, such as found in LCDM simulations, acting on an approximately 10Gyr
old star stream. The effects of a single set of halo substructure realizations
are shown for illustration, reserving a statistical comparison for another
study.Comment: ApJ revised version submitte
A new cubic theory of gravity in five dimensions: Black hole, Birkhoff's theorem and C-function
We present a new cubic theory of gravity in five dimensions which has second
order traced field equations, analogous to BHT new massive gravity in three
dimensions. Moreover, for static spherically symmetric spacetimes all the field
equations are of second order, and the theory admits a new asymptotically
locally flat black hole. Furthermore, we prove the uniqueness of this solution,
study its thermodynamical properties, and show the existence of a C-function
for the theory following the arguments of Anber and Kastor (arXiv:0802.1290
[hep-th]) in pure Lovelock theories. Finally, we include the
Einstein-Gauss-Bonnet and cosmological terms and we find new asymptotically AdS
black holes at the point where the three maximally symmetric solutions of the
theory coincide. These black holes may also possess a Cauchy horizon.Comment: 21 pages, no figures, V2: two appendices and some references added,
V3: New section on the generalization to arbitrary higher order. Analogy with
BHT new massive gravity Lagrangian made more precise, V4: Typos corrected. To
appear in CQ
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