19,690 research outputs found
Branching Ratios for the Decay of
Based on measurements the branching ratios for the decay of the recently
discovered dibaryon resonance into two-pion production channels and
into the channel are evaluated. Possibilities for a decay into the
isoscalar single-pion channel are discussed. Finally also the electromagnetic
decay of is considered
Examination of the Nature of the ABC Effect
Recently it has been shown by exclusive and kinematically complete
experiments that the appearance of a narrow resonance structure in
double-pionic fusion reactions is strictly correlated with the appearance of
the so-called ABC effect, which denotes a pronounced low-mass enhancement in
the -invariant mass spectrum. Whereas the resonance structure got its
explanation by the dibaryonic resonance, a satisfactory explanation
for the ABC effect is still pending. In this paper we discuss possible
explanations of the ABC effect and their consequences for the internal
structure of the dibaryon
Novel Six-Quark Hidden-Color Dibaryon States in QCD
The recent observation of a hadronic resonance in the proton-neutron
system with isospin and spin-parity raises the possibility
of producing other novel six-quark dibaryon configurations allowed by QCD. A
dramatic example of an exotic six-quark color-singlet system is the charge
, isospin I=3, state which couples strongly to
+ The width and decay properties of such
six-quark resonances could be regarded as manifestations of "hidden-color"
six-quark configurations, a first-principle prediction of QCD -- SU(3)-color
gauge theory for the deuteron distribution amplitude. Other implications and
possible future experiments are discussed
Limit Theorems For Quantum Walks Associated with Hadamard Matrices
We study a one-parameter family of discrete-time quantum walk models on the
line and in the xy-plane associated with the Hadamard walk. Weak convergence in
the long-time limit of all moments of the walker's pseudo-velocity on the line
and in the xy-plane is proved. Symmetrization on the line and in the xy-plane
is theoretically investigated, leading to the resolution of the
Konno-Namiki-Soshi conjecture in the special case of symmetrization of the
unbiased Hadamard walk on the line . A necessary condition for the existence of
a phenomenon known as localization is given
Acoustic oscillations of rapidly rotating polytropic stars. II. Effects of the Coriolis and centrifugal accelerations
Context: With the launch of space missions devoted to asteroseismology (like
COROT), the scientific community will soon have accurate measurements of
pulsation frequencies in many rapidly rotating stars.
Aims: The present work focuses on the effects of rotation on pulsations of
rapidly rotating stars when both the Coriolis and centrifugal accelerations
require a non-perturbative treatment.
Method: We develop a 2-dimensional spectral numerical approach which allows
us to compute acoustic modes in centrifugally distorted polytropes including
the full influence of the Coriolis force. This method is validated through
comparisons with previous studies, and the results are shown to be highly
accurate.
Results: In the frequency range considered and with COROT's accuracy, we
establish a domain of validity for perturbative methods, thus showing the need
for complete calculations beyond v.sin i = 50 km/s for a R = 2.3 R_\odot, M =
1.9 M_\odot polytropic star. Furthermore, it is shown that the main differences
between complete and perturbative calculations come essentially from the
centrifugal distortion.Comment: published in A&A, corrected minor mistakes and updated some
reference
Non-invasive Evaluation of Aortic Stiffness Dependence with Aortic Blood Pressure and Internal Radius by Shear Wave Elastography and Ultrafast Imaging
Elastic properties of arteries have long been recognized as playing a major
role in the cardiovascular system. However, non-invasive in vivo assessment of
local arterial stiffness remains challenging and imprecise as current
techniques rely on indirect estimates such as wall deformation or pulse wave
velocity. Recently, Shear Wave Elastography (SWE) has been proposed to
non-invasively assess the intrinsic arterial stiffness. In this study, we
applied SWE in the abdominal aortas of rats while increasing blood pressure
(BP) to investigate the dependence of shear wave speed with invasive arterial
pressure and non-invasive arterial diameter measurements. A 15MHz linear array
connected to an ultrafast ultrasonic scanner, set non-invasively, on the
abdominal aorta of anesthetized rats (N=5) was used. The SWE acquisition
followed by an ultrafast (UF) acquisition was repeated at different moment of
the cardiac cycle to assess shear wave speed and arterial diameter variations
respectively. Invasive arterial BP catheter placed in the carotid, allowed the
accurate measurement of pressure responses to increasing does of phenylephrine
infused via a venous catheter. The SWE acquisition coupled to the UF
acquisition was repeated for different range of pressure. For normal range of
BP, the shear wave speed was found to follow the aortic BP variation during a
cardiac cycle. A minimum of (5.060.82) m/s during diastole and a maximum
of (5.970.90) m/s during systole was measured. After injection of
phenylephrine, a strong increase of shear wave speed (13.855.51) m/s was
observed for a peak systolic arterial pressure of (19010) mmHg. A
non-linear relationship between shear wave speed and arterial BP was found. A
complete non-invasive method was proposed to characterize the artery with shear
wave speed combined with arterial diameter variations. Finally, the results
were validated against two parameters the incremental elastic modulus and the
pressure elastic modulus derived from BP and arterial diameter variations
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