Evaluation of White Striping prevalence and predisposing factors in broilers at slaughter

White striping ( WS: ) is an alteration of breast and thigh muscles of broiler chickens characterized by the presence of white striations parallel to the direction of muscle fibers. This study was performed to evaluate the prevalence and the predisposing factors to WS in commercial broilers of different weight reared in northern Italy. Fifty seven broiler flocks, including animals of medium- and heavy-weight, were grossly evaluated at slaughter for the presence of WS. For each flock, breeding data (mean BW at slaughter, ADG, sex, color of skin and fat, genetic line, age, antibiotic treatment, and prevalence of deep pectoral myopathy) were collected and statistically analyzed to assess their correlation with WS. Histology of breast fillets affected by different grades of WS was performed to evaluate potential differences between medium- and heavy-weight broilers. The overall prevalence of WS in medium- and heavy-weight broilers (mean BW 2.59 \ub1 0.13 kg and 3.64 \ub1 0.34 kg, respectively) was 70.2 \ub1 7.9% and 82.51 \ub1 8.5%, respectively, while the percentage of severe WS was 13.3 \ub1 7.1% and 25.7 \ub1 12.8%, respectively. A strong correlation was found between presence of WS, BW at slaughter, and ADG (Pearson correlation = 0.69, P < 0.01; Pearson correlation = 0.67, P < 0.01). WS also closely correlated with the prevalence of deep pectoral myopathy (Spearman's Rho slaughterhouse 1 = 0.74, Spearman's Rho slaughterhouse 2 = 0.51, P < 0.01). No correlation was found between genetics or sanitary status of the flock and WS. Histology confirmed that breasts with WS lesions were affected by a polyphasic degenerative and necrotizing myopathy, and that the lesions, as expected, were more severe in heavy-weight broilers. In conclusion, WS is a major concern in commercial meat poultry reared in Italy, affecting more severely heavier broilers, and it is mainly related to the BW and ADG of animals

Confinement regimes in simple magnetized toroidal plasmas

In the simple magnetized torus TORPEX (R = 1 m, a = 0.2 m), we explore experimentally the accessibility of a high confinement mode, which is predicted by theory for this configuration [P. Ricci, et al., Phys. Rev. Lett. 100, 225002 (2008)]. We consider different gases (H2, D, He, Ne, N2) and we measure the dependence of the temperature and density gradients upon the ratio γ/v’ExB (γ is the interchange linear growth rate and v’ExB is the velocity shear). We observe that gamma/v’ExB decreases from γ/v’ExB~6-7 for hydrogen to γ/v’ExB~0.3-0.4 for neon. Consistently with theory, temperature and density profiles steepen when γv’ExB drops below unity. The perpendicular particle flux is estimated by particle balance and measured using a multi-pin flux probe. First simulation results are presented with a global fluid code that solves the drift-reduced Braginskii equations in the whole TORPEX domain

Investigation of suprathermal ion transport in TORPEX

In burning plasmas, fast ions may be generated by ion cyclotron resonance heating, neutral beam injection and fusion reactions. Fast ions will be responsible for a significant fraction of plasma heating and, in some scenarios, non-inductive current drive. Fast ions are also present in natural plasmas, such as the solar corona or the magnetosphere, where they are presumably accelerated by wave-particle interactions. The high temperatures of tokamak plasmas and the huge spatial scale of astrophysical plasmas make measurements of the fast ion transport very challenging. Basic plasma devices offer the possibility to study the interaction between fast ions and plasma turbulence with easy access for diagnostics and well-establish plasma scenarios. Experiments in the linear plasma device LAPD have shown that fast ion transport is increased in presence of turbulent or coherent electrostatic waves and that it is generally nondiffusive [1]. Basic aspects of fast ion transport in ideal interchange-mode unstable plasmas are investigated in the simple toroidal plasma device TORPEX. The magnetic field configuration of TORPEX consists of a toroidal component (Bt = 75 mT) and a smaller vertical component (Bv = 2 mT), resulting in helical open field lines, with grad-B and curvature. With this magnetic geometry, the fast ion motion without plasma is a combination of the gyromotion along the field lines and the vertical grad-B and curvature drifts

Investigation of fast ion transport in TORPEX

Basic aspects of fast ion transport in ideal interchange-mode unstable plasmas are investigated in the simple toroidal plasma device TORPEX. Fast ions are generated by a miniaturized lithium 6+ ion source with energies up to 1 keV, and are detected using a double-gridded energy analyser mounted on a two-dimensional movable system in the poloidal cross-section. The signal-to-noise ratio is enhanced by applying a modulated biasing voltage to the fast ion source and using a synchronous detection scheme. An analogue lock-in amplifier has been developed, which allows removing the capacitive noise associated with the voltage modulation. We characterize vertical and radial transport of the fast ions, which is associated with the plasma turbulence. Initial experimental results show good agreement with numerical simulations of the fast ion transport in a global fluid simulation of the TORPEX plasma

Suprathermal ion transport theory and experiments in the SMT

Recent advances in the suprathermal ion diagnostic in the basic plasma experiment TORPEX have inspired our comprehensive theoretical study of suprathermal ion transport. TORPEX, an example of a simple magnetized toroidal plasma (SMT), is equipped with a flexible fast ion source and detector capable of exploring fast ion dynamics in a wide range of positions and energies. We simulate an ensemble of ion tracer trajectories as specified by ideal interchange-mode turbulence imported from a validated numerical simulation based on the drift-reduced Braginskii model. Using the variance of displacements, $\sigma^2(t) \sim t^{\gamma}$, we find that $\gamma$ depends strongly on suprathermal ion injection energy and the magnitude of turbulent fluctuations. When the beam interacts with the turbulence, we find the remarkable presence of three regimes of dispersion: superdiffusive, diffusive, and subdiffusive, depending on the energy of the suprathermal ions and the amplitude of the turbulent fluctuations. Results from the source on TORPEX are consistent with the theoretical predictions

Sheath boundary conditions for plasma fluid models

A new definition of the sheath edge is rigorously derived taking into account the kinetic properties of the plasma, and a consistent set of local sheath edge conditions is presented for the case of a magnetic field perpendicular to the wall. These local boundary conditions give explicit expressions for the ion velocity, the electron velocity, and the electron heat flux at the sheath edge, which can be easily implemented in a fluid code. It is shown that in the case of positive current to the wall, the commonly used Bohm's relations well aproximate the proposed boundary conditions, while large discrepancies are observed for negative currents. A fully kinetic PIC code simulating the plasma wall transition has been developed to validate these local relations, showing an excellent agreement with the theory. This work represents a first step towards a complete formulation of the sheath edge local boundary conditions for a general magnetic geometry

Plasma turbulence studies in TORPEX basic plasma pyhsics device: from concentric flux surfaces to single null X-points

TORPEX is a basic plasma physics device where a simple magnetized torus (SMT) is produced by adding a small vertical magnetic field to a main toroidal component, generating helical field lines. The SMT configuration features the main ingredients of a tokamak Scrape-Off Layer (SOL), namely density gradients in the presence of magnetic field curvature and gradient. Recently, a toroidal in-vessel copper conductor has been installed in the TORPEX device. A current up to 1kA can be driven in the toroidal conductor. This produces a poloidal magnetic field, which closes the field lines together with the toroidal field, resulting in a monotonic safety factor profile from 1 to 12 along the radial direction with an almost constant magnetic shear of 2. Several magnetic field geometries are accessible using the vertical field coils, from wall-limited plasmas with a SOL on the high-field side or low-field side, to single or double-null X-points as well as magnetic snowflakes. This way, more fusion relevant configurations of increasing complexity are achieved, while maintaining plasma parameters in ranges that allow a complete spatio-temporal diagnostic coverage across the plasma cross-section. Magnetic configurations with almost circular and concentric flux surfaces are considered for the analysis of plasma coherent structures. Quasi-coherent modes with a strong poloidal asymmetry are measured. A dominant localization on the bad-curvature region of the plasma volume (low field side) suggests a ballooning nature for these instabilities. A spectral characterization at the position of maximum fluctuation amplitudes is performed, including measurements of the power spectral density, indicating mode frequencies in the range 15-30 kHz. Measurements of vertical and toroidal correlations for several values of the poloidal magnetic field have been performed, allowing us to calculate the poloidal and toroidal mode-numbers. Field aligned modes with a toroidal mode number n=1 are identified. This is being compared with the numerical results obtained with the linear version of the Global Braginskii Solver (GBS) to assess the nature of the observed dominant instabilities. Initial measurements of plasma turbulence in TORPEX plasmas with a single null Xpoint will also be discussed, including analysis of the blob dynamics in this configuration performed using imaging techniques and conditional average sampling

Methodology for turbulence code validation: Quantification of simulation-experiment agreement and application to the TORPEX experiment

A methodology for plasma turbulence code validation is discussed, focusing on quantitative assessment of the agreement between experiments and simulations. The present work extends the analysis carried out in a previous paper [P. Ricci et al., Phys. Plasmas 16, 055703 (2009)] where the validation observables were introduced. Here, it is discussed how to quantify the agreement between experiments and simulations with respect to each observable, how to define a metric to evaluate this agreement globally, and-finally-how to assess the quality of a validation procedure. The methodology is then applied to the simulation of the basic plasma physics experiment TORPEX [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)], considering both two-dimensional and three-dimensional simulation models. [doi: 10.1063/1.3559436