339 research outputs found
Parity doubling in particle physics
Parity doubling in excited hadrons is reviewed. Parity degeneracy in hadrons
was first experimentally observed 40 years ago. Recently new experimental data
on light mesons caused much excitement and renewed interest to the phenomenon,
which still remains to be enigmatic. The present retrospective review is an
attempt to trace the history of parity doubling phenomenon, thus providing a
kind of introduction to the subject. We begin with early approaches of 1960s
(Regge theory and dynamical symmetries) and end up with the latest trends
(manifestations of broader degeneracies and AdS/QCD). We show the evolution of
various ideas about parity doubling. The experimental evidence for this
phenomenon is scrutinized in the non-strange sector. Some experiments of 1960s
devoted to the search for missing non-strange bosons are re-examined and it is
argued that results of these experiments are encouraging from the modern
perspective.Comment: Version to appear in Int. J. Mod. Phys. A, 63 pages, 9 figure
Veneziano like amplitude as a test for AdS/QCD models
The high energy asymptotics of QCD correlation functions is often used as a
test for bottom-up holographic models. Since QCD is not strongly coupled in the
ultraviolet domain, such a test may look questionable. We propose that the sum
over resonance poles emerging in correlators of a bottom-up model should
reproduce the structure of a Veneziano like amplitude at zero momentum transfer
assuming equivalence of spin and radial states in the latter. This requires a
five-dimensional background that suppresses the ultraviolet part in the
effective action of a model. We give examples of emerging low-energy
holographic models.Comment: 9 pages, accepted by the European Physical Journal C. arXiv admin
note: substantial text overlap with arXiv:1102.274
Features of radiation changes in electrical properties of InAlN/GaN HEMTs
The effect of the proton, electron, gamma - rays, and fast neutron irradiation on the parameters of InAlN/Ga
About the possibility of five-dimensional effective theories for low-energy QCD
The AdS/QCD models suggest an interesting idea that the effective theory of
low-energy QCD may be formulated as a 5-dimensional field theory in the weak
coupling regime in which the fifth coordinate plays a role of inverse energy
scale. Taking the point of view that this is just an efficient parametrization
of the non-perturbative dynamics of strong interactions, we discuss on a
qualitative level an alternative possibility for a simpler 5-dimensional
parametrization of main phenomena in the low-energy QCD. We propose to
interpret the effect of chiral symmetry breaking as an effective appearance of
compactified extra dimension with the radius of the order of inverse scale of
chiral symmetry breaking. Following some heuristic arguments two dual scenarios
for the emergence of the excited light mesons are introduced: In the first
scenario, the meson resonances are interpreted as the effects of Kaluza-Klein
excitations of quarks inside mesons, in the second one, as the formation of
gluon strings wound around the compactified dimension an appropriate number of
times. Matching of these scenarios permits to express the slope of radial Regge
trajectories through the order parameters of the chiral symmetry breaking, with
the compactification radius being excluded. This example shows qualitatively
that the extra dimension may play an auxiliary role providing a short way for
deriving new relations.Comment: 11 pages, accepted by Eur. Phys. J.
Optimization of Inotropic Support in Victims with Polytrauma and Acute Heart Failure
Objective: to evaluate the impact of ultrasound-guided nerve imaging on the efficiency and safety of supraclavicular brachial plexus block. Subjects and methods. Sixty-five patients underwent supraclavicular brachial plexus block. According to the method of nerve identification, all the patients were allocated to one of two groups: 1) Kulenkampff’s block, by identifying the nerves by a nerve stimulator (n=30); 2) supraclavicular block, by identifying the nerves by ultrasound scanning (n=35). Anesthesia was carried out with a local anesthetic solution containing 20 ml of 2% lidocaine and 10 ml of 0.5% bupivacaine (a total of 30 ml). Results. There is evidence for the high efficiency (97.1%) of ultrasound-guided nerve imaging and its safety (no multiple attempts to verify nerves and complications) as compared to the Kulenkampff supraclavicular block using neurostimulation to identify the plexus (p<0.05). Conclusion. The authors’ modified ultrasound-guided imaging in performing the brachial plexus block helps define nerve localization and observe the placement of a needle against the anatomic structures as it is advanced. Local anesthetic spread observed by ultrasound scanning confirms the precise location of the needle tip. Key words: ultrasound-guided nerve imaging, brachial plexus, efficiency of anesthesia, complication, supra-clavicular approach
Application of bent crystals at IHEP 70-GeV accelerator to enhance the efficiency of its usage
Bent crystal was extracting 70-GeV protons with average intensity 4*10^11 (as
measured in external beamline) per spill of 1.6 s duration, in parallel to the
simultaneous work of two internal targets in the accelerator ring. An
additional crystal, placed in the external beamline, was deflecting a small
part of the extracted beam with intensity 10^7 protons toward another physics
experiment. Crystal-extracted beam had a typical size of 4 mm by 4 mm fwhm at
the end of the external beamline. Measurements for the extraction efficiency
and other characteristics at the simultaneous work of four experimental set-ups
are presented. With crystal working in the above-said regime during one month,
no degradation of channeling was observed. The studies of extraction efficiency
have been continued with new crystals.Comment: 6pp. Presented at EPAC 200
Relation of the thermodynamic parameter of disordering with the width of structure factor and defect concentration in a metallic glass
In this work, we show that above the glass transition there exists a strong
unique interrelationship between the thermodynamic parameter of disorder of a
metallic glass derived using its excess entropy, diffraction measure of
disorder given by the width of the X-ray structure factor and defect
concentration derived from shear modulus measurements. Below the glass
transition, this relationship is more complicated and depends on both
temperature and thermal prehistory.Comment: 6 pages, 2 Figure
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