4,269 research outputs found
The integrable quantum group invariant A_{2n-1}^(2) and D_{n+1}^(2) open spin chains
A family of A_{2n}^(2) integrable open spin chains with U_q(C_n) symmetry was
recently identified in arXiv:1702.01482. We identify here in a similar way a
family of A_{2n-1}^(2) integrable open spin chains with U_q(D_n) symmetry, and
two families of D_{n+1}^(2) integrable open spin chains with U_q(B_n) symmetry.
We discuss the consequences of these symmetries for the degeneracies and
multiplicities of the spectrum. We propose Bethe ansatz solutions for two of
these models, whose completeness we check numerically for small values of n and
chain length N. We find formulas for the Dynkin labels in terms of the numbers
of Bethe roots of each type, which are useful for determining the corresponding
degeneracies. In an appendix, we briefly consider D_{n+1}^(2) chains with other
integrable boundary conditions, which do not have quantum group symmetry.Comment: 47 pages; v2: two references added and minor change
Why Adolescent Girls Play Basketball in Australia and its Meaning for them
The potential of organized sport to contribute to the health and wellbeing of young people justifies concern about their participation in it. While most research focuses on barriers and drop out, this article reports on a study that adopted a positive approach. Conducted in a large basketball club in Melbourne, Australia, it focused on what kept adolescent girls, aged 13-16 in one team. It identified two main factors contributing toward making basketball enjoyable for the six girls in the study and which kept them playing. They were: (1) relationships within the team and (2) having a strong sense of learning and improvement
Disc mechanical characteristics : construction of a finite element mathematical model, first results
Computational mechanics is an invaluable tool to analyze biomechanical systems, either in healthy or degenerative conditions, and to improve our understanding on the events that can trigger trauma or diseases, to design new medical devices to restore working conditions, or even to point out treatment techniques.
Numerical methods in general, and the Finite Elements Analysis (FEA) in particular, if properly built and used, can allow an inside view, a rigorous analysis and a qualitative study of any assumption, frequently too much difficult or even impossible to achieve with any in-vivo or in-vitro experimental technique.
An Intervertebral Disc (IVD) is a functionally-oriented construction of several soft tissues, supporting a wide range of dynamic and static loads that generate complex stress fields, which experimental study and understanding of its biomechanical behavior is of an enormous complexity.
On the one hand, human’s in-vivo study is almost impossible – due to the high degree of uncertainty in applied loads, geometric variability of individuals, complex surrounding musculoskeletal interactions, the role played by electro-chemical phenomena like osmolarity, etc – and post-mortem studies hardly provides accurate information to allow a clear and precise characterization and transposition to in-vivo biomechanics. On the other hand, due to that intrinsic complexity of the IVD, an accurate biomechanical model cannot easily be achieved. It is rather a step-by-step task where, although there are still many open questions, an important effort is being done to bring to the FEA the multi-physics behavior, and the complex interactions between them, in order to accurately model the IVD’s constitutive performance.
This work is focused in the most relevant issues and phenomena that shall be taken into account in the development of an accurate biomechanical FEA model of the IVD, either in healthy or degenerated states
Heat transfer coefficients from Newtonian and non-Newtonian fluids flowing in laminar regime in a helical coil
This study aimed to carry out experimental work to obtain, for Newtonian and non-Newtonian fluids, heat transfer coefficients, at constant wall temperature as boundary condition, in fully developed laminar flow inside a helical coil. The Newtonian fluids studied were aqueous solutions of glycerol, 25%, 36%, 43%, 59% and 78% (w/w) and the non-Newtonian fluids aqueous solutions of carboxymethylcellulose (CMC), a polymer, with concentrations 0.1%, 0.2%, 0.3%, 0.4% and 0.6% (w/w) and aqueous solutions of xanthan gum (XG), another polymer, with concentrations 0.1% and 0.2% (w/w). According to the rheological study performed, the polymer solutions had shear thinning behavior and different values of elasticity. The helical coil used has internal diameter, curvature ratio, length and pitch, respectively: 0.004575 m, 0.0263, 5.0 m and 11.34 mm. The Nusselt numbers for the CMC solutions are, on average, slightly higher than those for Newtonian fluids, for identical Prandtl and generalized Dean numbers. As outcome, the viscous component of the shear thinning polymer tends to potentiate the mixing effect of the Dean cells. The Nusselt numbers of the XG solutions are significant lower than those of the Newtonian solutions, for identical Prandtl and generalized Dean numbers. Therefore, the elastic component of the polymer tends to diminish the mixing effect of the Dean cells. A global correlation, for Nusselt number as a function of Péclet, generalized Dean and Weissenberg numbers for all Newtonian and non-Newtonian solutions studied, is presented
The muonic longitudinal shower profiles at production
In this paper the longitudinal profile of muon production along the shower
axis is studied. The characteristics of this distribution is investigated for
different primary masses, zenith angles, primary energies, and different high
energy hadronic models. It is found that the shape of this distribution
displays universal features similarly to what is known for the electromagnetic
profile. The relation between the muon production distribution and the
longitudinal electromagnetic evolution is also discussed
Observation of the Kohn anomaly near the K point of bilayer graphene
The dispersion of electrons and phonons near the K point of bilayer graphene
was investigated in a resonant Raman study using different laser excitation
energies in the near infrared and visible range. The electronic structure was
analyzed within the tight-binding approximation, and the
Slonczewski-Weiss-McClure (SWM) parameters were obtained from the analysis of
the dispersive behavior of the Raman features. A softening of the phonon
branches was observed near the K point, and results evidence the Kohn anomaly
and the importance of considering electron-phonon and electron-electron
interactions to correctly describe the phonon dispersion in graphene systems.Comment: 4 pages, 4 figure
Cerenkov angle and charge reconstruction with the RICH detector of the AMS experiment
The Alpha Magnetic Spectrometer (AMS) experiment to be installed on the
International Space Station (ISS) will be equipped with a proximity focusing
Ring Imaging Cerenkov (RICH) detector, for measurements of particle electric
charge and velocity. In this note, two possible methods for reconstructing the
Cerenkov angle and the electric charge with the RICH, are discussed. A
Likelihood method for the Cerenkov angle reconstruction was applied leading to
a velocity determination for protons with a resolution of around 0.1%. The
existence of a large fraction of background photons which can vary from event
to event, implied a charge reconstruction method based on an overall efficiency
estimation on an event-by-event basis.Comment: Proceedings submitted to RICH 2002 (Pylos-Greece
New methods to reconstruct and the energy of gamma-ray air showers with high accuracy in large wide-field observatories
Novel methods to reconstruct the slant depth of the maximum of the
longitudinal profile (\Xmax) of high-energy showers initiated by gamma-rays as
well as their energy () are presented. The methods were developed for
gamma rays with energies ranging from a few hundred GeV to TeV. An
estimator of \Xmax is obtained, event-by-event, from its correlation with the
distribution of the arrival time of the particles at the ground, or the signal
at the ground for lower energies. An estimator of is obtained,
event-by-event, using a parametrization that has as inputs the total measured
energy at the ground, the amount of energy contained in a region near to the
shower core and the estimated \Xmax.
Resolutions about and about for,
respectively, \Xmax and at energies are obtained,
considering vertical showers. The obtained results are auspicious and can lead
to the opening of new physics avenues for large wide field-of-view gamma-ray
observatories. The dependence of the resolutions with experimental conditions
is discussed.Comment: 11 pages; 15 figures, to appear in EPJ
The Estimation of the Effective Centre of Mass Energy in q-qbar-gamma Events from DELPHI
The photon radiation in the initial state lowers the energy available for the
ee collisions; this effect is particularly important at LEP2 energies
(above the mass of the Z boson). Being aligned to the beam direction, such
initial state radiation is mostly undetected. This article describes the
procedure used by the DELPHI experiment at LEP to estimate the effective
centre-of-mass energy in hadronic events collected at energies above the Z
peak. Typical resolutions ranging from 2 to 3 GeV on the effective
center-of-mass energy are achieved, depending on the event topology.Comment: 12 pages, 6 figure
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