Modulational instability in dispersion-kicked optical fibers

We study, both theoretically and experimentally, modulational instability in optical fibers that have a longitudinal evolution of their dispersion in the form of a Dirac delta comb. By means of Floquet theory, we obtain an exact expression for the position of the gain bands, and we provide simple analytical estimates of the gain and of the bandwidths of those sidebands. An experimental validation of those results has been realized in several microstructured fibers specifically manufactured for that purpose. The dispersion landscape of those fibers is a comb of Gaussian pulses having widths much shorter than the period, which therefore approximate the ideal Dirac comb. Experimental spontaneous MI spectra recorded under quasi continuous wave excitation are in good agreement with the theory and with numerical simulations based on the generalized nonlinear Schr\"odinger equation

Heteroclinic structure of parametric resonance in the nonlinear Schr\"odinger equation

We show that the nonlinear stage of modulational instability induced by parametric driving in the {\em defocusing} nonlinear Schr\"odinger equation can be accurately described by combining mode truncation and averaging methods, valid in the strong driving regime. The resulting integrable oscillator reveals a complex hidden heteroclinic structure of the instability. A remarkable consequence, validated by the numerical integration of the original model, is the existence of breather solutions separating different Fermi-Pasta-Ulam recurrent regimes. Our theory also shows that optimal parametric amplification unexpectedly occurs outside the bandwidth of the resonance (or Arnold tongues) arising from the linearised Floquet analysis

Solitary waves in the Nonlinear Dirac Equation

In the present work, we consider the existence, stability, and dynamics of solitary waves in the nonlinear Dirac equation. We start by introducing the Soler model of self-interacting spinors, and discuss its localized waveforms in one, two, and three spatial dimensions and the equations they satisfy. We present the associated explicit solutions in one dimension and numerically obtain their analogues in higher dimensions. The stability is subsequently discussed from a theoretical perspective and then complemented with numerical computations. Finally, the dynamics of the solutions is explored and compared to its non-relativistic analogue, which is the nonlinear Schr{\"o}dinger equation. A few special topics are also explored, including the discrete variant of the nonlinear Dirac equation and its solitary wave properties, as well as the PT-symmetric variant of the model

Long-Term Survival of Human Neural Stem Cells in the Ischemic Rat Brain upon Transient Immunosuppression

Understanding the physiology of human neural stem cells (hNSCs) in the context of cell therapy for neurodegenerative disorders is of paramount importance, yet large-scale studies are hampered by the slow-expansion rate of these cells. To overcome this issue, we previously established immortal, non-transformed, telencephalic-diencephalic hNSCs (IhNSCs) from the fetal brain. Here, we investigated the fate of these IhNSC's immediate progeny (i.e. neural progenitors; IhNSC-Ps) upon unilateral implantation into the corpus callosum or the hippocampal fissure of adult rat brain, 3 days after global ischemic injury. One month after grafting, approximately one fifth of the IhNSC-Ps had survived and migrated through the corpus callosum, into the cortex or throughout the dentate gyrus of the hippocampus. By the fourth month, they had reached the ipsilateral subventricular zone, CA1-3 hippocampal layers and the controlateral hemisphere. Notably, these results could be accomplished using transient immunosuppression, i.e administering cyclosporine for 15 days following the ischemic event. Furthermore, a concomitant reduction of reactive microglia (Iba1+ cells) and of glial, GFAP+ cells was also observed in the ipsilateral hemisphere as compared to the controlateral one. IhNSC-Ps were not tumorigenic and, upon in vivo engraftment, underwent differentiation into GFAP+ astrocytes, and β-tubulinIII+ or MAP2+ neurons, which displayed GABAergic and GLUTAmatergic markers. Electron microscopy analysis pointed to the formation of mature synaptic contacts between host and donor-derived neurons, showing the full maturation of the IhNSC-P-derived neurons and their likely functional integration into the host tissue. Thus, IhNSC-Ps possess long-term survival and engraftment capacity upon transplantation into the globally injured ischemic brain, into which they can integrate and mature into neurons, even under mild, transient immunosuppressive conditions. Most notably, transplanted IhNSC-P can significantly dampen the inflammatory response in the lesioned host brain. This work further supports hNSCs as a reliable and safe source of cells for transplantation therapy in neurodegenerative disorders

Technical Note: Rabbit welfare during electrical stunning and slaughter at a commercial abattoir

[EN] A total of 1020 crossbreed rabbits were individually examined to evaluate their welfare during electric stunning and slaughter in a commercial abattoir. Stunning (the position of electrodes and repetition of applications of current) and sticking (the position, length and depth of the cut) procedures were checked. The rabbits were monitored behaviourally from the application of the current to death. The stunning system was incorrectly applied one hundred and ten times (10.8%). Three rabbits failed to be stunned and were still conscious at sticking. Eighteen rabbits recovered before the onset of death, as shown by their corneal reflex and in a few cases, vocalization (n=3) and head movement (n=1) were observed. Corneal reflex seemed to be the best indicator of recovery at the abattoir.Rota Nodari, S.; Lavazza, A.; Candotti, P. (2009). Technical Note: Rabbit welfare during electrical stunning and slaughter at a commercial abattoir. World Rabbit Science. 17(3):163-167. doi:10.4995/wrs.2009.65616316717

Orbital stability: analysis meets geometry

International audienceWe present an introduction to the orbital stability of relative equilibria of Hamiltonian dynamical systems on (finite and infinite dimensional) Banach spaces. A convenient formulation of the theory of Hamiltonian dynamics with symmetry and the corresponding momentum maps is proposed that allows us to highlight the interplay between (symplectic) geometry and (functional) analysis in the proofs of orbital stability of relative equilibria via the so-called energy-momentum method. The theory is illustrated with examples from finite dimensional systems, as well as from Hamiltonian PDE's, such as solitons, standing and plane waves for the nonlinear Schrödinger equation, for the wave equation, and for the Manakov system

Efficacy of a new vaccine (Myco-Suivax\uae) against Mycoplasma hyopneumoniae under field conditions

Swine enzootic pneumonia is caused by a complex interaction between Mycoplasma hyopneumoniae (Mh), the primary infectious agent, environmental factors, and other infectious agents. In the last few years, the efficacy of numerous vaccines has been demonstrated in reducing losses deriving from enzootic pneumonia. The objective of the present study was to evaluate the field efficacy of a new vaccine (Myco-Suivax\uae, Fatro) administered at a single or double dose in the presence of disease, in an Italian farrow-to-finishing farm, where the long fattening cycle causes slaughter of swine at 160\u2013170 kg of live body weight (LBW) and 9\u201310 months of age. The experimental trial was conducted in a farrow-tofinishing farm of 730 sows situated in Northern Italy, where problems of enzootic pneumonia had been identified in growing pigs. Three consecutive homogeneous groups of 300 piglets each were included in the study; these were assigned at random to one of the following treatment groups: - Group A (double shot): vaccinated twice at 7 days of age and at weaning (25 days of age) at a dose of 1 ml; - Group B (one shot): vaccinated once at a dose of 2 ml on the day of the end of the weaning period (60 days of age); - Group C: control (no Mh vaccination). The efficacy of the vaccine was based primarily on the pulmonary lesions associated with respiratory disease, using the method described by Madec and Kobisch. The overall weights at the end of weaning and at slaughter were also recorded, together with feed consumption in the interval between end of weaning and slaughter, to calculate Average Daily Weight Gains (ADWG) and Feed Conversion Rate (FCR). Slaughter was performed, for pig movement restriction reasons (outbreaks of MVS in the Lombardia region in 2006-2007), between 10 and 11 months of age. The animals which died during the trial were subjected to necroscopic examination and laboratory investigations (PCR) to highlight the presence of Mh. All statistical analyses were performed using the software SPSS 12.0.0 (SPSS, 2003). Necroscopic findings and laboratory investigations highlighted the presence of M. hyopneumoniae in swine of all the treatment groups. Myco-Suivax\uae was able to reduce pulmonary lesions, decrease the number of animals which died and improve weight gain and the FCR in both groups subjected to vaccination. The results appear particularly significant taking into account the late slaughter age (160\u2013170 kg of LBW) and 9\u201310 months of age), in which pulmonary lesions due to M. hyopneumoniae have mainly regressed and where growth tends to at slow down. In the specific field situation in which the trial was conducted, the one shot vaccination, performed at 60 days of age, was the one able to supply the best zootechnical results