Photoproduction and Radiative Decay of Spin 1/2 and 3/2 Pentaquarks

We study photoproduction and radiative decays of pentauqarks paying particular attention to the differences between spin-1/2 and spin-3/2, positive and negative parities of pentaquarks. Detailed study of these processes can not only give crucial information about the spin, but also the parity of pentaquarks.Comment: 14 pages, 7 figure

qq-Virasoro Algebra and the Point-Splitting

It is shown that a particular $q$-deformation of the Virasoro algebra can be interpreted in terms of the $q$-local field $\Phi (x)$ and the Schwinger-like point-splitted Virasoro currents, quadratic in $\Phi (x)$. The $q$-deformed Virasoro algebra possesses an additional index $\alpha$, which is directly related to point-splitting of the currents. The generators in the $q$-deformed case are found to exactly reproduce the results obtained by probing the fields $X(z)$ (string coordinate) and $\Phi (z)$ (string momentum) with the non-splitted Virasoro generators and lead to a particular representation of the $SU_q (1,1)$ algebra characterized by the standard conformal dimension $J$ of the field. Some remarks concerning the $q$-vertex operator for the interacting $q$-string theory are made.Comment: 17 pages, Late

Obesity and Metabolic Syndrome in Korea

In Korea, a person with a body mass index (BMI) ≥25 kg/m2 is considered obese, and a person with a BMI ≥30 kg/m2 is classified as severely obese. Central obesity is defined as a waist circumference ≥90 cm for Korean men and ≥85 cm for Korean women. Recent epidemiologic data show that the prevalence of severe obesity and metabolic syndrome is steadily increasing. These epidemics increased morbidity and mortality of type 2 diabetes, cardiovascular diseases, and obesity-related cancers such as breast, colorectal, and other cancers in Korea. Decreased physical activity, increased fat and alcohol consumption, heavy smoking, and stress/depressed mood are the primary modifiable life-style risk factors for Koreans. Recently, public health interventions to encourage life-style changes have shown promising results in reducing the prevalence of severe obesity and metabolic syndrome

Quark Delocalization, Color Screening Model and Nucleon-Baryon Scattering

We apply the quark delocalization and color screening model to nucleon-baryon scattering. A semi-quantitative fit to N-N, N-Lambda and N-Sigma phase shifts and scattering cross sections is obtained without invoking meson exchange. Quarks delocalize reasonably in all of the different flavor channels to induce effective nucleon-baryon interactions with both a repulsive core and with an intermediate range attraction in the cases expected.Comment: 14 pp. RevTeX plus 13 figs.ps, submitted to Phys. Rev.

Triquark correlations and pentaquarks in a QCD sum rule approach

The role of quark correlations in the description of hadron dynamics in many domains of physics, from low energy dynamics to very hot(dense) systems, is being appreciated. Strong correlations of two quarks (diquark) have been widely investigated in this respect. Recently, we have proposed a dynamical scheme to describe the $\Theta^+$ pentaquark in which also three quark correlations (triquark) were instrumental in producing a low mass exotic state. We perform a study, within the QCD sum rule approach including OPE and direct instanton contributions, of triquark correlations and obtain two quasi-bound light $ud\bar{s}$ color quark clusters of 800 MeV and 930 MeV respectively.Comment: 11 pages, 9 figures, corrected typos, reference added, introduction and conclusions modified slightl

Stresses in cement mantles of hip replacements: effect of femoral implant sizes, body mass index and bone quality

The effects of femoral prosthetic heads of diameters 22 and 28 mm were investigated on the stability of reconstructed hemi-pelves with cement mantles of thicknesses 1-4 mm and different bone qualities. Materialise medical imaging package and I-Deas finite element (FE) software were used to create accurate geometry of a hemi-pelvis from CT-scan images. Our FE results show an increase in cement mantle stresses associated with the larger femoral head. When a 22 mm femoral head is used on acetabulae of diameters 56 mm and above, the probability of survivorship can be increased by creating a cement mantle of at least 1 mm thick. However, when a 28 mm femoral head is used, a cement mantle thickness of at least 4 mm is needed. Poor bone quality resulted in an average 45% increase in the tensile stresses of the cement mantles, indicating resulting poor survivorship rate

Light-Front Approach for Pentaquark Strong Decays

Assuming the two diquark structure for the pentaquark state as advocated in the Jaffe-Wilczek model, we study the strong decays of light and heavy parity-even pentaquark states using the light-front quark model in conjunction with the spectator approximation. The narrowness of the Theta width is ascribed to the p-wave configuration of the diquark pair. Taking the Theta width as a benchmark, we estimate the rates of the strong decays Xi_{3/2}-- to Xi- pi-, Sigma- K-, Sigma_{5c}0 to D_s- p, D_{s0}*- p and Xi_{5c}0 to D_s- Sigma+, D_{s0}^{*-} Sigma+ with Sigma_{5c} Xi_{5c} being antisextet charmed pentaquarks and D_{s0}* a scalar strange charmed meson. The ratio of Gamma(P_c to Baryon D_{s0}*)/Gamma(P_c to Baryon D_s) is very useful for verifying the parity of the antisextet charmed pentaquark P_c. It is expected to be of order unity for an even parity P_c and much less than one for an odd parity pentaquark.Comment: 24 pages, 2 figure