Polymerase chain reaction detection of rabbit DNA in food and animal feed

[EN] A polymerase chain reaction (PCR) based on oligonucleotide primers targeting the mitochondrial 12S rRNA gene was developed for the specific identification of rabbit DNA (Oryctolagus cuniculus) in food and feedstuffs. The specificity of the primers was verified by PCR analysis of DNA from 32 non-target species including mammals, birds, fish, and plant species. Analysis of experimental mixtures demonstrated the presence of rabbit-derived materials in the range of 0.1-100%. Prolonged heat treatment (up to 133ºC for 20 min at 300 kPa) applied to rabbit muscle/oats binary mixtures did not affect the performance of the method, which could therefore be said to be very useful for the accurate identification of rabbit materials in products submitted to denaturing technologies when other methods are not suitable.This study was supported by Grant Nº. AGL 2007-60077 from the Spanish Ministerio de Educación y Ciencia and the Programa de Vigilancia Sanitaria S-0505/AGR/000265 of the Comunidad de Madrid (Spain). Irene Martín is the recipient of a fellowship from the Universidad Complutense de Madrid (Spain). Violeta Fajardo and María Rojas are recipients of fellowships from the Ministerio de Educación y Ciencia (Spain).Martín, I.; García, T.; Fajardo, V.; Rojas, M.; Pegels, N.; Hernández, P.; González, I.... (2009). Polymerase chain reaction detection of rabbit DNA in food and animal feed. World Rabbit Science. 17(1):27-34. doi:10.4995/wrs.2009.667273417

An integral method for solving nonlinear eigenvalue problems

We propose a numerical method for computing all eigenvalues (and the corresponding eigenvectors) of a nonlinear holomorphic eigenvalue problem that lie within a given contour in the complex plane. The method uses complex integrals of the resolvent operator, applied to at least $k$ column vectors, where $k$ is the number of eigenvalues inside the contour. The theorem of Keldysh is employed to show that the original nonlinear eigenvalue problem reduces to a linear eigenvalue problem of dimension $k$. No initial approximations of eigenvalues and eigenvectors are needed. The method is particularly suitable for moderately large eigenvalue problems where $k$ is much smaller than the matrix dimension. We also give an extension of the method to the case where $k$ is larger than the matrix dimension. The quadrature errors caused by the trapezoid sum are discussed for the case of analytic closed contours. Using well known techniques it is shown that the error decays exponentially with an exponent given by the product of the number of quadrature points and the minimal distance of the eigenvalues to the contour

Algivory in food webs of three temperate Andean rivers

Food web analyses have been fundamental in understanding community organization and ecosystem functioning. To date, a number of studies demonstrate that stream food webs depend to a large extent on allochthonous detritus, but there are more recent studies that show a high degree of autochthony. Our food-web study was carried out in three Andean rivers (Coilaco, Guampoe and Trancura) within the catchment area of Toltén River in southern Chile. Based on the analyses of 4251 invertebrate gut contents, we found that these Andean stream food webs are dominated by herbivores (range: 50-73% of all species) supported by a species-rich algal (basal) component, and characterized by a low proportion of omnivores (range: 8-27% of all species) and predatory species (range: 10-24%). Significant differences in the number of feeding links of the herbivores Meridialis diguillina and Antarctoperla michaelseni and the omnivore Smicridea chilensis were found between seasons. The spring herbivore Aubertoperla sp. showed significant differences between rivers. S.chilensis fed on 50 different prey items as compared with the herbivores whose maximum number of links ranged between 37 and 40. Web sizes ranged between 93 and 131 species and the proportion of top species was distinctly lower than those of basal (up to 0.651 in Coilaco River) and intermediate species. Direct connectance (links per species2) values were low and similar among rivers (range: 0.051-0.074), whereas mean food chain length ranged between 2.23 and 2.90. The distributions of web property values from the Andean rivers differed from those previously published. In contrast to previous predictions, mean food chain length in these Andean streams displayed a scale-invariant pattern across different web sizes, but it was significantly related to the proportion of intermediate species. © 2011 The Authors. Journal compilation © 2011 Ecological Society of Australia

A simple and efficient numerical scheme to integrate non-local potentials

As nuclear wave functions have to obey the Pauli principle, potentials issued from reaction theory or Hartree-Fock formalism using finite-range interactions contain a non-local part. Written in coordinate space representation, the Schrodinger equation becomes integro-differential, which is difficult to solve, contrary to the case of local potentials, where it is an ordinary differential equation. A simple and powerful method has been proposed several years ago, with the trivially equivalent potential method, where non-local potential is replaced by an equivalent local potential, which is state-dependent and has to be determined iteratively. Its main disadvantage, however, is the appearance of divergences in potentials if the wave functions have nodes, which is generally the case. We will show that divergences can be removed by a slight modification of the trivially equivalent potential method, leading to a very simple, stable and precise numerical technique to deal with non-local potentials. Examples will be provided with the calculation of the Hartree-Fock potential and associated wave functions of 16O using the finite-range N3LO realistic interaction.Comment: 8 pages, 2 figures, submitted to Eur. Phys. J.

The trajectory of a range of commonly captured symptoms with standard care in people with kidney failure receiving haemodialysis: consideration for clinical trial design

Background Despite the recognized high symptom prevalence in haemodialysis population, how these symptoms change over time and its implications for clinical practice and research is poorly understood. Methods Prevalent haemodialysis patients in the SHAREHD trial reported 17 POS-S Renal symptoms (none, mild, moderate, severe and overwhelming) at baseline, 6, 12 and 18 months. To assess the prevalence change at population level in people reporting moderate or worse symptoms at baseline, the absolute change in prevalence was estimated using multi-level mixed effects probit regression adjusting for age, sex, time on haemodialysis and Charlson Comorbidity Score. To assess changes at individual level, the proportion of people changing their symptom score every 6 months was estimated. Results Five hundred fifty-two participants completed 1725 questionnaires at four timepoints. Across all 17 symptoms with moderate or worse symptom severity at baseline, the majority of the change in symptom prevalence at population level occurred in the ‘severe’ category. The absolute improvement in prevalence of the ‘severe’ category was ≤ 20% over 18 months in eleven of the seventeen symptoms despite a large degree of relatively balanced movement of individuals in and out of severe category every six months. Examples include depression, skin changes and drowsiness, which had larger proportion (75–80%) moving in and out of severe category each 6 months period but  20% were observed in six symptoms, driven by a 9 to 18% difference between movement in and movement out of severe category. All symptoms had > 50% of people in severe group changing severity within 6 months. Conclusions Changes in the severity of existing symptoms under standard care were frequent, often occurring within six months. Certain symptoms exhibited clinically meaningful shifts at both the population and individual levels. This highlighted the need to consider improvements in symptom severity when determining sample size and statistical power for trials. By accounting for potential symptom improvements with routine care, researchers can design trials capable of robustly detecting genuine treatment effects, distinguishing them from spontaneous changes associated with standard haemodialysis

Scaling and self-averaging in the three-dimensional random-field Ising model

We investigate, by means of extensive Monte Carlo simulations, the magnetic critical behavior of the three-dimensional bimodal random-field Ising model at the strong disorder regime. We present results in favor of the two-exponent scaling scenario, $\bar{\eta}=2\eta$, where $\eta$ and $\bar{\eta}$ are the critical exponents describing the power-law decay of the connected and disconnected correlation functions and we illustrate, using various finite-size measures and properly defined noise to signal ratios, the strong violation of self-averaging of the model in the ordered phase.Comment: 8 pages, 6 figures, to be published in Eur. Phys. J.

Observation of hard scattering in photoproduction events with a large rapidity gap at HERA

Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a function of the $\gamma p$ centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a two-jet structure with each jet having a transverse energy greater than 4 GeV. For the two-jet events, little energy flow is found outside the jets. This observation is consistent with the hard scattering of a quasi-real photon with a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe