Stabilization of space–time laser instability through the finite transverse extension of pumping

We investigate the space–time dynamics of a homogeneously broadened single-mode laser when diffraction is taken into account. It is well known that such a laser displays instability when pumping reaches the second laser threshold. We show that the laser dynamics can be stabilized by pumping in a domain of finite width. The analysis of stationary solutions to the Maxwell–Bloch equations (evanescent waves, travelling waves, localized solutions) allows the stabilization mechanism to be explained

Feed size and texture influence propionic and butyric acid concentrations and Escherichia coli populations in the pig gastrointestinal tract

Natural approaches are now being considered to replace antimicrobials to reduce the risk of antimicrobial resistance development. This has put the new emphasis on using diet to control bacterial infections in pigs, some of which having recently demonstrated a zoonotic disease potential

Nonlinear Analysis of Irregular Variables

The Fourier spectral techniques that are common in Astronomy for analyzing periodic or multi-periodic light-curves lose their usefulness when they are applied to unsteady light-curves. We review some of the novel techniques that have been developed for analyzing irregular stellar light or radial velocity variations, and we describe what useful physical and astronomical information can be gained from their use.Comment: 31 pages, to appear as a chapter in `Nonlinear Stellar Pulsation' in the Astrophysics and Space Science Library (ASSL), Editors: M. Takeuti & D. Sasselo

Analyse de dynamiques spatio-temporelles d’un laser

La dynamique spatio-temporelle d’un système laser avec diffraction est étudiée. La correspondance entre la structure du portrait de phase et l’organisation relative desdéfauts topologiques dans les diagrammes spatio-temporels est clairement mise en évidence. Ainsi, une dynamique de type chaos toroïdal est associée à des défauts apparaissant périodiquement (dans l’espace et dans le temps). En revanche, il n’y a plus de périodicité des défauts sur les diagrammes spatio-temporels lorsque le régime est un chaos développé

Risk factors associated with presence of Salmonella in pigs in Canada

Carriers of Salmonella in finishing pigs are believed to be a main source of carcass and pork contamination at the slaughterhouse and during meat processing. To better control the presence of Salmonella at the farm and slaughter, it is important to adequately identify on-farm risk factors associated with presence of these bacteria in animals

Impact of mash feeding versus pellets on propionic/butyric acid levels and on total Escherichia coli load in the gastrointestinal tract of growing pigs

Feed characteristics may influence the bacterial community composition and metabolic activities in the pig gastrointestinal tract, known to be associated with positive effects on the gut. Use of mash feed is associated with reduced Salmonella excretion, but little is known of its effect on the Escherichia coli population or of the mechanism of action. Our objectives were to assess the effect of feed texture combined with feed particle size on VFA profiles and levels, total E. coli count, and the presence of genes encoding virulence factors of pathogenic E. coli strains in the digestive tract along with their impact on pig performance of fattening pigs. Pigs (n = 840) on a commercial farm received mash or pellet diets of different particle sizes during the fattening period. Caecal and colon contents from 164 pigs were sampled at the slaughterhouse for enumeration of E. coli by quantitative PCR (qPCR) and for VFA quantification by capillary gas chromatography. The yccT gene was used to enumerate total E. coli. Improved pig performances associated with pellet texture and a 500-μm size were observed. Caecal (P = 0.02) and colon (P < 0.01) propionic acid concentrations were lower for pigs receiving pellet rather than mash feed. Similarly, caecal (P = 0.01) and colon (P < 0.001) butyric acid concentrations were also lower for pigs receiving pellet rather than mash feed, as determined by capillary gas chromatography. Moreover, caecal (P = 0.03) and colon (P < 0.001) butyric acid concentrations were higher for pigs receiving a feed with a 1,250-μm particle size rather than a 500-μm particle size. On the other hand, total caecal and colon E. coli levels were higher for pigs receiving pellet feed than for those receiving mash feed. For total E. coli enumeration, caecal (P < 0.01) and colon (P < 0.01) yccT gene copies were higher for pigs receiving pellet rather than mash feed. No effect of particle size on fatty acid concentrations or on E. coli numbers was observed. Virulence gene quantification revealed no trend. Taken together, results showed that mash feed is associated with lower growth performance but with favorable intestinal changes linked to VFA levels and E. coli reduction in the intestine

PHIL photoinjector test line

LAL is now equiped with its own platform for photoinjectors tests and Research and Developement, named PHIL (PHotoInjectors at LAL). This facility has two main purposes: push the limits of the photoinjectors performances working on both the design and the associated technology and provide a low energy (MeV) short pulses (ps) electron beam for the interested users. Another very important goal of this machine will be to provide an opportunity to form accelerator physics students, working in a high technology environment. To achieve this goal a test line was realised equipped with an RF source, magnets and beam diagnostics. In this article we will desrcibe the PHIL beamline and its characteristics together with the description of the first two photoinjector realised in LAL and tested: the ALPHAX and the PHIN RF Guns

Detection of Hepatitis E virus in swine using real-time RT-PCR

The zoonotic transmtsswn potential of Hepatitis E virus (HEY) is now widely recognized. Swine represents the main animal reservoir for this virus in many countries, including Canada. In recent years, different real-time RT-PCR assays were developed and proposed as reliable and sensitive detection methods. However, the quality of extracted RNA, presence of inhibitors and RN ase contamination of the samples may impact on the detection results obtained with these molecular methods. The aim of this study was to evaluate the use of a sample process control (SPC) within a real-time RT-PCR assay for the detection ofHEV. This TaqMan multiplex assay was afterwards used to evaluate the viral load ofHEV in organs, tissues and excreta of normal pigs at slaughter. HEY RNA was detected in at least one sample from 14 out of the 43 animals tested (32.6 %). HEV was present in lymph nodes (25.6%), bladder (23.3%), liver (20.9%), bile (18.6%), feces (13.9%), tonsils (7.0%) and plasma (2.3%) but was undetected in loins

Forces During Bacteriophage DNA Packaging and Ejection

The conjunction of insights from structural biology, solution biochemistry, genetics and single molecule biophysics has provided a renewed impetus for the construction of quantitative models of biological processes. One area that has been a beneficiary of these experimental techniques is the study of viruses. In this paper we describe how the insights obtained from such experiments can be utilized to construct physical models of processes in the viral life cycle. We focus on dsDNA bacteriophages and show that the bending elasticity of DNA and its electrostatics in solution can be combined to determine the forces experienced during packaging and ejection of the viral genome. Furthermore, we quantitatively analyze the effect of fluid viscosity and capsid expansion on the forces experienced during packaging. Finally, we present a model for DNA ejection from bacteriophages based on the hypothesis that the energy stored in the tightly packed genome within the capsid leads to its forceful ejection. The predictions of our model can be tested through experiments in vitro where DNA ejection is inhibited by the application of external osmotic pressure

Chaos in free electron laser oscillators

The chaotic nature of a storage-ring Free Electron Laser (FEL) is investigated. The derivation of a low embedding dimension for the dynamics allows the low-dimensionality of this complex system to be observed, whereas its unpredictability is demonstrated, in some ranges of parameters, by a positive Lyapounov exponent. The route to chaos is then explored by tuning a single control parameter, and a period-doubling cascade is evidenced, as well as intermittence.Comment: Accepted in EPJ