12,760 research outputs found
Obesity management: Update on orlistat
Over the past 20 years obesity has become a worldwide concern of frightening proportion. The World Health Organization estimates that there are over 400 million obese and over 1.6 billion overweight adults, a figure which is projected to almost double by 2015. This is not a disease restricted to adults – at least 20 million children under the age of 5 years were overweight in 2005 (WHO 2006). Overweight and obesity lead to serious health consequences including coronary artery disease, stroke, type-2 diabetes, heart failure, dyslipidemia, hypertension, reproductive and gastrointestinal cancers, gallstones, fatty liver disease, osteoarthritis and sleep apnea (Padwal et al 2003)
Spinning test particles and clock effect in Schwarzschild spacetime
We study the behaviour of spinning test particles in the Schwarzschild
spacetime. Using Mathisson-Papapetrou equations of motion we confine our
attention to spatially circular orbits and search for observable effects which
could eventually discriminate among the standard supplementary conditions
namely the Corinaldesi-Papapetrou, Pirani and Tulczyjew. We find that if the
world line chosen for the multipole reduction and whose unit tangent we denote
as is a circular orbit then also the generalized momentum of the
spinning test particle is tangent to a circular orbit even though and
are not parallel four-vectors. These orbits are shown to exist because the spin
induced tidal forces provide the required acceleration no matter what
supplementary condition we select. Of course, in the limit of a small spin the
particle's orbit is close of being a circular geodesic and the (small)
deviation of the angular velocities from the geodesic values can be of an
arbitrary sign, corresponding to the possible spin-up and spin-down alignment
to the z-axis. When two spinning particles orbit around a gravitating source in
opposite directions, they make one loop with respect to a given static observer
with different arrival times. This difference is termed clock effect. We find
that a nonzero gravitomagnetic clock effect appears for oppositely orbiting
both spin-up or spin-down particles even in the Schwarzschild spacetime. This
allows us to establish a formal analogy with the case of (spin-less) geodesics
on the equatorial plane of the Kerr spacetime. This result can be verified
experimentally.Comment: IOP macros, eps figures n. 2, to appear on Classical and Quantum
gravity, 200
The Rapidly Rotating, Hydrogen Deficient, Hot Post-Asymptotic Giant Branch Star ZNG 1 in the Globular Cluster M5
We report observations of the hot post-asymptotic giant branch star ZNG 1 in
the globular cluster M5 (NGC 5904) with the Far Ultraviolet Spectroscopic
Explorer (FUSE). From the resulting spectrum, we derive an effective
temperature T_eff = 44300 +/- 300 K, a surface gravity log g = 4.3 +/- 0.1, a
rotational velocity v sin i = 170 +/- 20 km/s, and a luminosity log (L/L_sun) =
3.52 +/- 0.04. The atmosphere is helium-rich (Y = 0.93), with enhanced carbon
(2.6% by mass), nitrogen (0.51%) and oxygen (0.37%) abundances. The spectrum
shows evidence for a wind with terminal velocity near 1000 km/s and an
expanding shell of carbon- and nitrogen-rich material around the star. The
abundance pattern of ZNG 1 is suggestive of the ``born-again'' scenario,
whereby a star on the white-dwarf cooling curve undergoes a very late shell
flash and returns to the AGB, but the star's rapid rotation is more easily
explained by a previous interaction with a binary companion.Comment: 8 pages, 2 PostScript figures, Latex with emulateapj5. Accepted for
publication in ApJ Letter
A direct proof of the CSW rules
Using recursion methods similar to those of Britto, Cachazo, Feng and Witten
(BCFW) a direct proof of the CSW rules for computing tree-level gluon
amplitudes is given.Comment: 11 pages, uses axodraw.st
Dynamics of test bodies with spin in de Sitter spacetime
We study the motion of spinning test bodies in the de Sitter spacetime of
constant positive curvature. With the help of the 10 Killing vectors, we derive
the 4-momentum and the tensor of spin explicitly in terms of the spacetime
coordinates. However, in order to find the actual trajectories, one needs to
impose the so-called supplementary condition. We discuss the dynamics of
spinning test bodies for the cases of the Frenkel and Tulczyjew conditions.Comment: 11 pages, RevTex forma
On-Shell Unitarity Bootstrap for QCD Amplitudes
We describe the recently developed on-shell bootstrap for computing one-loop
amplitudes in non-supersymmetric theories such as QCD. The method combines the
unitarity method with loop-level on-shell recursion. The unitarity method is
used to compute cut-containing parts of amplitudes, and on-shell recursion is
used for the remaining rational terms.Comment: 10 pages, 9 figures, write-up of talks given by Z. Bern and D. A.
Kosower at Loops & Legs 2006, Eisenach, Germany; v2: added referenc
Hydro-without-Hydro Framework for Simulations of Black Hole-Neutron Star Binaries
We introduce a computational framework which avoids solving explicitly
hydrodynamic equations and is suitable to study the pre-merger evolution of
black hole-neutron star binary systems. The essence of the method consists of
constructing a neutron star model with a black hole companion and freezing the
internal degrees of freedom of the neutron star during the course of the
evolution of the space-time geometry. We present the main ingredients of the
framework, from the formulation of the problem to the appropriate computational
techniques to study these binary systems. In addition, we present numerical
results of the construction of initial data sets and evolutions that
demonstrate the feasibility of this approach.Comment: 16 pages, 7 figures. To appear in the Classical and Quantum Gravity
special issue on Numerical Relativit
From Yang-Mills Lagrangian to MHV Diagrams
We prove the equivalence of a recently suggested MHV-formalism to the
standard Yang-Mills theory. This is achieved by a formally non-local change of
variables. In this note we present the explicit formulas while the detailed
proofs are postponed to a future publication.Comment: Latex,11 pages, minor changes, reference added, version to appear in
JHE
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