A study of the distribution of Salmonella serovars in an integrated pig company

A total of 3220 faecal samples from 161 pig farms (rearing and finishing units) belonging to an integrated pig enterprise were collected over a period of 18 months. Salmonella was found in 630 (19.5%) of the samples. At the farm level, 111 of 161 premises (69%) had at least one Salmonella- positive sample. 72.8% of rearing units and 66.6% of finishing units were positive for Salmonella; 61.4% of isolates were S. Typhimurium (387/630 isolates), and 25% of isolates were S. Derby (157/630). S. Panama, which was the third most common serovar (4.9% of isolates), is rarely found in pigs or other animals in the UK and appeared to be largely specific to this company, being found in the multiplier herd as well

Using discrete Darboux polynomials to detect and determine preserved measures and integrals of rational maps

In this Letter we propose a systematic approach for detecting and calculating preserved measures and integrals of a rational map. The approach is based on the use of cofactors and Discrete Darboux Polynomials and relies on the use of symbolic algebra tools. Given sufficient computing power, all rational preserved integrals can be found. We show, in two examples, how to use this method to detect and determine preserved measures and integrals of the considered rational maps.Comment: 8 pages, 1 Figur

Trees and superintegrable Lotka-Volterra families

To any tree on $n$ vertices we associate an $n$-dimensional Lotka-Volterra system with $3n-2$ parameters and prove it is superintegrable, i.e. it admits $n-1$ functionally independent integrals. We also show how these systems can be reduced to an ($n-1$)-dimensional system which is superintegrable and solvable by quadratures.Comment: 13 pages, 2 figure

Linear Darboux polynomials for Lotka-Volterra systems, trees and superintegrable families

We present a method to construct superintegrable $n$-component Lotka-Volterra systems with $3n-2$ parameters. We apply the method to Lotka-Volterra systems with $n$ components for $1 < n < 6$, and present several $n$-dimensional superintegrable families. The Lotka-Volterra systems are in one-to-one correspondence with trees on $n$ vertices.Comment: 14 pages, 4 figure