Numerical study of axisymmetric vortex breakdowns

Axisymmetric flow of rotating stream analyzed to determine conditions allowing isolated vortex breakdown to develo

The Epidemiology of Johne\u27s Disease

What does the epidemiologist concern himself with when studying an outbreak of Johne\u27s disease? When the disease is first diagnosed in a herd many facts must be determined. First, how many animals are infected? This is difficult to determine as will be seen in the section on diagnosis. Second, where did the disease come from and what caused the breakdown? Since the natural incubation period has been determined (Hole, 1958), the investigator cannot look at past records of the herd and determine the source of the disease

Thermal and electromagnetic properties of 166-Er and 167-Er

The primary gamma-ray spectra of 166-Er and 167-Er are deduced from the (3-He,alpha gamma) and (3-He,3-He' gamma) reaction, respectively, enabling a simultaneous extraction of the level density and the gamma-ray strength function. Entropy, temperature and heat capacity are deduced from the level density within the micro-canonical and the canonical ensemble, displaying signals of a phase-like transition from the pair-correlated ground state to an uncorrelated state at Tc=0.5 MeV. The gamma-ray strength function displays a bump around E-gamma=3 MeV, interpreted as the pygmy resonance.Comment: 21 pages including 2 tables and 11 figure

Level densities and γ\gamma-strength functions in 148,149^{148,149}Sm

The level densities and $\gamma$-strength functions of the weakly deformed $^{148}$Sm and $^{149}$Sm nuclei have been extracted. The temperature versus excitation energy curve, derived within the framework of the micro canonical ensemble, shows structures, which we associate with the break up of Cooper pairs. The nuclear heat capacity is deduced within the framework of both the micro canonical and the canonical ensemble. We observe negative heat capacity in the micro canonical ensemble whereas the canonical heat capacity exhibits an S-shape as function of temperature, both signals of a phase transition. The structures in the $\gamma$-strength functions are discussed in terms of the pygmy resonance and the scissors mode built on exited states. The samarium results are compared with data for the well deformed $^{161,162}$Dy, $^{166,167}$Er and $^{171,172}$Yb isotopes and with data from (n,$\gamma$)-experiments and giant dipole resonance studies.Comment: 12 figure

Dicarbonyl stress and beta-cell dysfunction

Methylglyoxal may be involved in the early stages of decline in glucose tolerance and decline in pancreatic beta-cell function leading to type 2 diabetes. Methylglyoxal and methylglyoxal-modified proteins increase during short-term increases in glucose concentration, infusion of exogenous methylglyoxal in rats and mice impaired glucose tolerance and glyoxalase 1 (Glo1) prevented beta-cell toxicity. We investigated the role of methylglyoxal and protein glycation on beta-cell function and the development of diabetes, with focus on the interactions of cells with the extracellular matrix. Impairments in adhesion of MIN6 insulinoma cells to methylglyoxal-glycated collagen IV were assessed in vitro using atomic force microscopy force spectroscopy and methylglyoxal glycation adducts within the pancreas visualised by immunostaining. Minimal glycation of collagen IV at integrin binding sites impaired binding of MIN6 cells in vitro and resulted in a 91% decrease in the energy necessary to detach the cells from collagen. Evidence from high fat diet fed mice showed that the methylglyoxal concentration of the pancreas was increased in the insulin resistant, pre-diabetic state with methylglyoxal-derived glycation adducts within the pancreas predominantly localised to the extracellular matrix in vivo. We conclude that glycation of extracellular matrix collagen IV likely impairs adhesion of beta-cells to the extracellular matrix in pre-diabetes in vivo and may thereby contribute to beta-cell glucotoxicity and dysfunction with progression to type 2 diabetes mellitus

Gamma-ray strength function and pygmy resonance in rare earth nuclei

The gamma-ray strength function for gamma energies in the 1-7 MeV region has been measured for 161,162-Dy and 171,172-Yb using the (3-He,alpha gamma) reaction. Various models are tested against the observed gamma-ray strength functions. The best description is based on the Kadmenskii, Markushev and Furman E1 model with constant temperature and the Lorentzian M1 model. A gamma-ray bump observed at E_gamma=3 MeV is interpreted as the so-called pygmy resonance, which has also been observed previously in (n,gamma) experiments. The parameters for this resonance have been determined and compared to the available systematics.Comment: 11 pages, including 4 figures and 2 table

Photon data shed new light upon the GDR spreading width in heavy nuclei

A global study of the electric dipole strength in and below the isovector giant dipole resonance (GDR) is presented for mass numbers A>80. It relies on the recently established remarkably good match between data for the nuclear photo effect to novel photon scattering data covering the region below the neutron emission threshold as well as by average resonance neutron capture (ARC). From the wide energy coverage of these data the correlation of the GDR spreading width with energy can be studied with remarkable accuracy. A clear sensitivity to details of the nuclear shape, i.e. the beta- and gamma-deformations, is demonstrated. Based hereon a new parameterization of the energy dependence of the nuclear electric-dipole strength is proposed which - with only two new parameters - allows to describe the dipole strength in all heavy nuclei with A>80. Although it differs significantly from previous parameterizations it holds for spherical, transitional, triaxial and well deformed nuclei. The GDR spreading width depends in a regular way on the respective resonance energy, but it is independent of the photon energy.Comment: accepted by Phys. Lett. B after minor modification

Large N_c, Constituent Quarks, and N, Delta Charge Radii

We show how one may define baryon constituent quarks in a rigorous manner, given physical assumptions that hold in the large-N_c limit of QCD. This constituent picture gives rise to an operator expansion that has been used to study large-N_c baryon observables; here we apply it to the case of charge radii of the N and Delta states, using minimal dynamical assumptions. For example, one finds the relation r_p^2 - r_{Delta^+}^2 = r_n^2 - r_{Delta^0}^2 to be broken only by three-body, O(1/N_c^2) effects for any N_c.Comment: 15 pages, 1 eps figure. Version to appear in Phys. Rev.

Large enhancement of radiative strength for soft transisitons in the quasicontinuum

Radiative strength functions (RSFs) for the 56,57-Fe nuclei below the separation energy are obtained from the 57-Fe(3-He,alpha gamma)56-Fe and 57-Fe(3-He,3-He' gamma)57-Fe reactions, respectively. An enhancement of more than a factor of ten over common theoretical models of the soft (E_gamma ~< 2 MeV) RSF for transitions in the quasicontinuum (several MeV above the yrast line) is observed. Two-step cascade intensities with soft primary transitions from the 56-Fe(n,2gamma)57-Fe reaction confirm the enhancement.Comment: 4 pages including 3 figure