706 research outputs found
Sprouty1 regulates reversible quiescence of a self-renewing adult muscle stem cell pool during regeneration.
Satellite cells are skeletal muscle stem cells capable of self-renewal and differentiation after transplantation, but whether they contribute to endogenous muscle fiber repair has been unclear. The transcription factor Pax7 marks satellite cells and is critical for establishing the adult satellite cell pool. By using a lineage tracing approach, we show that after injury, quiescent adult Pax7(+) cells enter the cell cycle; a subpopulation returns to quiescence to replenish the satellite cell compartment, while others contribute to muscle fiber formation. We demonstrate that Sprouty1 (Spry1), a receptor tyrosine kinase signaling inhibitor, is expressed in quiescent Pax7(+) satellite cells in uninjured muscle, downregulated in proliferating myogenic cells after injury, and reinduced as Pax7(+) cells re-enter quiescence. We show that Spry1 is required for the return to quiescence and homeostasis of the satellite cell pool during repair. Our results therefore define a role for Spry1 in adult muscle stem cell biology and tissue repair
Primary gas thermometry by means of laser-absorption spectroscopy: Determination of the Boltzmann constant
We report on a new optical implementation of primary gas thermometry based on
laser absorption spectrometry in the near infrared. The method consists in
retrieving the Doppler broadening from highly accurate observations of the line
shape of the R(12) transition in
CO gas at thermodynamic equilibrium. Doppler width measurements as a
function of gas temperature, ranging between the triple point of water and the
gallium melting point, allowed for a spectroscopic determination of the
Boltzmann constant with a relative accuracy of .Comment: Submitted to Physical Review Letter
New Relations for Gauge-Theory Amplitudes
We present an identity satisfied by the kinematic factors of diagrams
describing the tree amplitudes of massless gauge theories. This identity is a
kinematic analog of the Jacobi identity for color factors. Using this we find
new relations between color-ordered partial amplitudes. We discuss applications
to multi-loop calculations via the unitarity method. In particular, we
illustrate the relations between different contributions to a two-loop
four-point QCD amplitude. We also use this identity to reorganize gravity tree
amplitudes diagram by diagram, offering new insight into the structure of the
KLT relations between gauge and gravity tree amplitudes. This can be used to
obtain novel relations similar to the KLT ones. We expect this to be helpful in
higher-loop studies of the ultraviolet properties of gravity theories.Comment: 40 pages, 7 figures, RevTex, v2 minor correction
Relation between the pole and the minimally subtracted mass in dimensional regularization and dimensional reduction to three-loop order
We compute the relation between the pole quark mass and the minimally
subtracted quark mass in the framework of QCD applying dimensional reduction as
a regularization scheme. Special emphasis is put on the evanescent couplings
and the renormalization of the epsilon-scalar mass. As a by-product we obtain
the three-loop on-shell renormalization constants Zm(OS) and Z2(OS) in
dimensional regularization and thus provide the first independent check of the
analytical results computed several years ago.Comment: 22 page
Precise mass-dependent QED contributions to leptonic g-2 at order alpha^2 and alpha^3
Improved values for the two- and three-loop mass-dependent QED contributions
to the anomalous magnetic moments of the electron, muon, and tau lepton are
presented. The Standard Model prediction for the electron (g-2) is compared
with its most precise recent measurement, providing a value of the
fine-structure constant in agreement with a recently published determination.
For the tau lepton, differences with previously published results are found and
discussed. An updated value of the fine-structure constant is presented in
"Note added after publication."Comment: 6 pages, 1 figure. v2: New determination of alpha presented (based on
the recent electron g-2 measurement). v3: New formulae added in Sec.IIB. v4:
Updated value of alpha presente
Heavy-to-heavy quark decays at NNLO
Details of a recent calculation of O(alpha_s^2) corrections to the decay b ->
c,l,nu_l, taking into account the c-quark mass, are described. Construction of
the expansion in the mass ratio m_c/m_b as well as the evaluation of new
four-loop master integrals are presented. The same techniques are applicable to
the muon decay, mu -> e,nu_mu,anti-nu_e. Analytical results are presented, for
the physical cases as well as for a model with purely-vector couplings.Comment: 11 page
QCD Corrections to the Radiative Decay B -> X_s gamma
In this short review, the calculation of the next-to-next-to-leading order
QCD corrections to the inclusive radiative decay B -> X_s gamma is described. I
summarize the salient features of the calculational framework adopted, discuss
the results obtained in the last few years, and indicate the technical tools
that made the NNLO calculations possible. I conclude by comparing the current
NNLO theoretical estimate for the branching ratio with the experimental
measurement and by briefly discussing the size and origin of the residual
theoretical uncertainty.Comment: 18 pages, 7 figures. Invited review for Modern Physics Letters
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