Basic Problems in Playing the Cornet

After having spent a number of years in the teaching profession, the writer has become aware of the need for a study dealing with the specific and technical problems in playing the cornet

Topography of Aortic Bifurcation in a Black Kenyan Population

Topography of aortic bifurcation is important for gynaecologists, surgeons and radiologists operating in the retroperitoneal area, in order for them to minimize vascular injury. It also influences the occurrence of aortic-iliac atherosclerosis. It shows ethnic variations, but data from African populations are scarce. This study therefore investigated the topography of aortic bifurcation in a black Kenyan population by dissection of 106 cadavers. After removal of abdominal viscera, peritoneum, fibrofatty connective tissue, inferior vena cava was removed to expose the termination of abdominal aorta. Vertebral level, angle and asymmetry of bifurcation were recorded. Data were analysed by SPSS version 17.0 for windows and are presented in tables and bar charts. All aortae terminated by bifurcating into 2 common iliac arteries. The most common level of bifurcation was L4 (73.6%). It bifurcated below L4 in 22.7% of the cases. Mean angle of bifurcation was 55.20 (range 23 – 780); 55.60 in males and 54.30 in females. Mean bifurcation asymmetry was 4.4 (range 0 – 23). Topography of aortic bifurcation in the black Kenyan population varies from conventional descriptions on over 20% of the individuals studied. Surgeons and radiologists must be aware of this to avoid inadvertent vascular injury. Higher bifurcation angles and asymmetry than those reported for Caucasian and Indo Asian populations suggest higher vulnerability to abdominal aortic atherosclerosis. Preoperative evaluation of terminal aorta, and follow up for atherosclerosis are recommended

Baryon Octet magnetic moments in χ\chiPT: More on the importance of the Decuplet

We address the impact of treating the decuplet of spin-3/2 baryons as an explicit degree of freedom in the chiral expansion of the magnetic moments of the octet of spin-1/2 baryons. We carry out a complete calculation of the octet moments to O(1/\lamchic), including decuplet contributions to the chiral loops. In contrast to results of previous analyses, we find that inclusion of the decuplet preserves the convergence behavior of the chiral expansion implied by power counting arguments.Comment: 17 pages, 2 figures. Includes axodraw.sty needed for figures Minor typos correcte

Effective field theory and the quark model

We analyze the connections between the quark model (QM) and the description of hadrons in the low-momentum limit of heavy-baryon effective field theory in QCD. By using a three-flavor-index representation for the effective baryon fields, we show that the ``nonrelativistic'' constituent QM for baryon masses and moments is completely equivalent through O(m_s) to a parametrization of the relativistic field theory in a general spin--flavor basis. The flavor and spin variables can be identified with those of effective valence quarks. Conversely, the spin-flavor description clarifies the structure and dynamical interpretation of the chiral expansion in effective field theory, and provides a direct connection between the field theory and the semirelativistic models for hadrons used in successful dynamical calculations. This allows dynamical information to be incorporated directly into the chiral expansion. We find, for example, that the striking success of the additive QM for baryon magnetic moments is a consequence of the relative smallness of the non-additive spin-dependent corrections.Comment: 25 pages, revtex, no figure

High Energy Hadron-Nucleus Cross Sections and Their Extrapolation to Cosmic Ray Energies

Old models of the scattering of composite systems based on the Glauber model of multiple diffraction are applied to hadron-nucleus scattering. We obtain an excellent fit with only two free parameters to the highest energy hadron-nucleus data available. Because of the quality of the fit and the simplicity of the model it is argued that it should continue to be reliable up to the highest cosmic ray energies. Logarithmic extrapolations of proton-proton and proton-antiproton data are used to calculate the proton-air cross sections at very high energy. Finally, it is observed that if the exponential behavior of the proton-antiproton diffraction peak continues into the few TeV energy range it will violate partial wave unitarity. We propose a simple modification that will guarantee unitarity throughout the cosmic ray energy region.Comment: 8 pages, 9 postscript figures. This manuscript replaces a partial manuscript incorrectly submitte

Analysis of dynamical corrections to baryon magnetic moments

We present and analyze QCD corrections to the baryon magnetic moments in terms of the one-, two-, and three-body operators which appear in the effective field theory developed in our recent papers. The main corrections are extended Thomas-type corrections associated with the confining interactions in the baryon. We investigate the contributions of low-lying angular excitations to the moments quantitatively and show that they are completely negligible. When the QCD corrections are combined with the non-quark model contributions of the meson loops, we obtain a model which describes the moments within a mean deviation of 0.04 $\mu_N$. The nontrivial interplay of the two types of corrections to the quark-model moments is analyzed in detail, and explains why the quark model is so successful. In the course of these calculations, we parametrize the general spin structure of the $j={1/2}^+$ baryon wave functions in a form which clearly displays the symmetry properties and the internal angular momentum content of the wave functions, and allows us to use spin-trace methods to calculate the many spin matrix elements which appear in the expressions for the moments. This representation may be useful elsewhere.Comment: 32 pages, 3 figures, submitted to Phys. Rev.

Octet magnetic moments and the Coleman-Glashow sum rule violation in the chiral quark model

Baryon octet magnetic moments when calculated within the chiral quark model, incorporating the orbital angular momentum as well as the quark sea contribution through the Cheng-Li mechanism, not only show improvement over the non relativistic quark model results but also gives a non zero value for the right hand side of Coleman-Glashow sum rule. When effects due to spin-spin forces between constituent quarks as well as `mass adjustments' due to confinement are added, it leads to an excellent fit for the case of p, \Sigma^+, \Xi^o and violation of Coleman-Glashow sum rule, whereas in almost all the other cases the results are within 5% of the data.Comment: 5 RevTeX pages, accepted for publication in PRD(Rapid Communication

Baryon Magnetic Moments in a QCD-based Quark Model with loop corrections

We study meson loop corrections to the baryon magnetic moments starting from a QCD-based quark model derived earlier in a quenched approximation to QCD. The model reproduces the standard quark model with extra corrections for the binding of the quarks. The loop corrections are necessary to remove the quenching. Our calculations use heavy baryon perturbation theory with chiral baryon-meson couplings and a form factor characterizing the structure of baryons as composite particles. The form factor reflects soft wave function effects with characteristic momenta $\approx 400$ MeV, well below the usual chiral cutoff of $\approx 1$ GeV. The resulting model involves only three parameters, the quark moments $\mu_u$ and $\mu_s$ and a parameter $\lambda$ that sets the momentum scale in the wavefunctions. We find that this approach substantially improves the agreement between the theoretical and experimental values of the octet baryon magnetic moments, with an average difference between the theoretical and experimental moments of 0.05$\mu_N$. An extension to the decuplet states using the same input predicts a moment of 1.97 $\mu_N$ for the $\Omega^-$ hyperon, in excellent agreement with the measured moment of $2.02\pm0.05 \mu_N$.Comment: 23 pages, 3 figure