Search

The Wnt Inhibitory Factor 1 (Wif1), known to inhibit Wnt signaling pathways, is composed of a WIF domain and five EGF-like domains (EGF-LDs) involved in protein interactions. Despite the presence of a potential O-fucosylation site in its EGF-LDs III and V, the O-fucose sites occupancy has never been demonstrated for WIF1. In this study, a phylogenetic analysis on the distribution, conservation and evolution of Wif1 proteins was performed, as well as biochemical approaches focusing on O-fucosylation sites occupancy of recombinant mouse WIF1. In the monophyletic group of gnathostomes, we showed that the consensus sequence for O-fucose modification by Pofut1 is highly conserved in Wif1 EGF-LD III while it was more divergent in EGF-LD V. Using click chemistry and mass spectrometry, we demonstrated that mouse WIF1 was only modified with a non-extended O-fucose on its EGF-LD III. In addition, a decreased amount of mouse WIF1 in the secretome of CHO cells was observed when the O-fucosylation site in EGF-LD III was mutated. Based on sequence comparison and automated protein modeling, we suggest that the absence of O-fucose on EGF-LD V of WIF1 in mouse and probably in most gnathostomes, could be related to EGF-LD V inability to interact with POFUT1.

The performance of induction magnetometers, in terms of resolution, depends both on the induction sensor and the electronic circuit. To investigate accurately the sensor noise sources, an induction sensor, made of a ferrite ferromagnetic core, is combined with a dedicated low voltage and current noise preamplifier, designed in CMOS 0.35 μm technology. A modelling of the contribution of the ferromagnetic core to the noise through the complex permeability formalism is performed. Its comparison with experimental measurements highlight another possible source for the dominating noise near the resonance.

The possibility of Gyrodactylus salaris infection of wild North Atlantic salmon Salmo salar spreading to new rivers poses a major threat in Norway. This freshwater parasite can survive for some time in brackish water, and it has been suggested that smolts leaving infected rivers could transport vital parasites to new rivers. A Monte Carlo simulation model was used to estimate the risk that infected smolts would ascend a new river. Data from an infected watercourse in Norway, where the salmon population is maintained constant by cultivation, were used. The model included information on prevalence of infection, hydrographical conditions, survival of G. salaris in brackish water, fish population characteristics, and smolt behaviour during seaward migration. The annual risk was estimated for 3 neighbouring rivers situated at different distances from the index river. For the nearest river, which shares the same brackish water zone with the index river, the model estimated an annual risk of 31% that at least 1 infected smolt would ascend this river. The results of the simulation were highly sensitive to the water salinity along the migration route. For the other rivers, the annual risk was lower than 0.5%. Risk was positively correlated with the number of fish leaving the index river, indicating control of this number as a possible tool in risk management.

International audience; The Sodium-cooled fast neutron reactor ASTRID is currently under design and development in France. Traditional ECCO/ERANOS fast reactor code system used for ASTRID core design calculations relies on multi-group JEFF-3.1.1 data library. To gauge the use of ENDF/B-VII.0 and JEFF-3.1.1 nuclear data libraries in the fast reactor applications, two recent OECD/NEA computational benchmarks specified by Argonne National Laboratory were calculated. Using the continuous-energy TRIPOLI-4 Monte Carlo transport code, both ABR-1000 MWth MOX core and metallic (U-Pu) core were investigated. Under two different fast neutron spectra and two data libraries, ENDF/B-VII.0 and JEFF-3.1.1, reactivity impact studies were performed. Using JEFF-3.1.1 library under the BOEC (Beginning of equilibrium cycle) condition, high reactivity effects of 808 ± 17 pcm and 1208 ± 17 pcm were observed for ABR-1000 MOX core and metallic core respectively. To analyze the causes of these differences in reactivity, several TRIPOLI-4 runs using mixed data libraries feature allow us to identify the nuclides and the nuclear data accounting for the major part of the observed reactivity discrepancies.

The sections in this article are 1 Introduction 2 Time Series and Embeddings 3 Chaos in the Parameter Modulated Laser 4 Control of Chaotic Flow 5 Summary and Outlook 6 Biographical Sketch Related Articles

The transition from quasiperiodicity to chaos in an NMR laser with delayed feedback is investigated both experimentally and numerically. We concentrate on the low-delay-time region where stable tori arise either from a sequence of two Hopf bifurcations or from an ``interaction'' between mutually transversal unstable limit cycles. Transitions to chaos via intermittency and crises have been observed, as well as the ``fractalization'' of tori.

Experimental observations and computer simulations of locked states in an infinite-dimensional periodically Q-modulated NMR laser with feedback are presented. Arnold tongues (AT's) were observed both for a harmonic and an anharmonic (square-wave) modulation. The width of selected AT's were significantly larger for the anharmonic modulation than for the harmonic modulation. In addition, the AT's were observed to split into regimes of locking to different fundamental limit cycles as the modulation amplitude was increased. Significant deviations of the locking behavior from predictions of the one-dimensional circle map were observed. The experimental results agreed in an excellent way with simulations with a phenomenological Bloch-Kirchhoff model with a heuristic relaxation term and consequently present an exemplary test for the model.

The competition between noise and coherence near an instability (laser threshold, bifurcation point, crisis, collision) of an NMR laser is explored experimentally and numerically.

The NMR laser may easily be driven into chaos by either modulation of parameter or by delayed feedback. Fractal dimensions and Lyapunov exponents of chaotic attractors are defined both from experimental and computed time series.

A case of community-acquired, culture-negative, infective endocarditis was diagnosed in a 57-year-old construction worker. Small, pleomorphic gram-negative rods were seen in Brown-Hopps tissue gram stains and Warthin-Starry silver stains. The organism was identified as Rochalimaea henselae by polymerase chain reaction amplification and sequencing of the 16S rDNA gene sequence. This is the first report of infective endocarditis caused by R henselae.

The usefulness of the Ott-Grebogi-Yorke control method is demonstrated by stabilizing a chaotic NMR-laser system around an unstable period-one orbit. We have used a six-dimensional delay-coordinate embedding technique in order to fully determine the stability properties of the orbit controlled. Our analysis yields small time-dependent perturbations of the system quality factor capable to perform real-time control.

Within the wide field of nonlinear dynamics we investigate temporal and spatial behavior of electromagnetic systems. A strange type of laser, the nuclear magnetic resonance (NMR) laser, shows truly chaotic behavior and is therefore ideally suited to analyze experimentally and theoretically a variety of temporal nonlinear effects. Of particular interest is the analysis of its strange attractors in terms of unstable periodic orbits. For the extension of our research from the NMR laser (representing a purely temporal system described by the Bloch-Kirchhoff ordinary differential equations) to spatial and spatiotemporal systems, we chose, as a three-dimensional dynamic system, polarized laser beams interacting nonlinearly with sodium atoms. Among other effects, we have observed beam bouncing, beam splitting, and beam switching. This can be well described by partial differential equations for beam propagation derived from the Schrodinger equation and the Maxwell equations. An intuitive explanation is given in terms of intensity and polarization patterns formed by optical-pumping-induced mutual refractive index modifications between polarized resonant laser beams.

The solid-state ruby nuclear magnetic resonance (NMR) laser shows sequence of instabilities if amplitude or frequency of an external driving signal are swept. With the parametrically modulated NMR laser sequence of period-doubling bifurcations and subsequent transitions to a chotic behaviour were found which are typical of the Feigenbaum scenoario for a route to chaos. In the same system intermittency was observed indicating the presence of the Pomeau-Mannaeville scenario. Chaotic bands were found also along the route to injection-locking where the NMR laser is driven by a stable external oscillator with its frequency slighty detuned from the NMR frequency. Side-products of these investigations of chaotic dynamics are observations with respect to the frequency-pushing of two lasers and the use of a period-doubling laser as small-signal detection.

Radio wave amplification by stimulated emission of radiation (NMR laser) was observed in Al/sub 2/O/sub 3/:Cr/sup 3 +/ (ruby) with the /sup 27/Al spin system pumped to an inverted Zeeman state by means of dynamic nuclear polarization (DNP) and with an LC circuit tuned to the NMR transitions. A theory is developed which combines standard Bloch equations with the dynamic equations of a heat-reservoir model for the spin dynamics. Experimental data concerning the relaxation and polarization mechanisms in the nonradiant state are presented, and the parameters of the reservoir model are determined. In accord with these results, dynamic NMR laser equations for different modes of operation (continuous or pulsed) are derived from which the threshold of the NMR laser, its critical behavior near threshold, and its transient response after Q-switch tuning can be calculated. The agreement between theory and experiments in the super-radiant state reflects unambiguously the interplay between nuclear-spin relaxation, DNP, spin fluctuations, and the self-induced ordering of the /sup 27/Al spins perpendicular to the applied field. In particular, the results highlight the decisive role of the electronic dipole-dipole system in the spin and NMR laser dynamics of ruby. Special emphasis is placed on the close relationship between themore » NMR laser, as a system far from thermal equilibrium which shows the phenomenon of cooperative self-organization, and a system at thermal equilibrium which undergoes a second-order phase transition. Thus, the rotating nuclear-spin magnetization is treated as an order parameter.« less

The dynamic properties of the ruby NMR laser are discussed from the point of view of synergetics. The authors present a theoretical approach together with the experimental verification. The cooperative features of the instabilities and the disorder-order transitions far from thermal equilibrium of the ruby NMR laser are described by means of order parameters and their dynamic equations, which are generalized Bloch equations. The heat-reservoir description of the conventional spin dynamics in ruby is thereby taken into account. The theory is applied to the free-running NMR laser with its threhold, the critical narrowing of cw NMR lines below threshold, and the steady-state output above threshold. The theory is then extended to the driven NMR laser where an external resonant rf field is applied to form, together with the self-induced radiation field, a competitive- or cooperative-field configuration. The authors present data concerning bistability and hysteresis of the driven NMR laser; in particular, its first-order-type phase transitions from a competitive- to a cooperative-field configuration are discussed. Finally, a novel pulsation mode of the ruby NMR laser is described.

We present experimental observations along the roads to chaos of a tuned low-Q solid state spin-flip NMR laser (raser) which, according to our earlier work , should show the universal Feigenbaum scenario under certain conditions. The free running ruby raser is periodically perturbed by modulating one of its physical parameters. For example, one may modulate the pumping magnetization sinusoidally with the angular frequency Ω close to the eigenfrequency of the linearized raser equations, typically f = Ω/2π ≃ 30 Hz.

The Feature Issue on Instabilities in Active Optical Media of the Journal of the Optical Society of America B [1]shows the increasing interest in nonlinear phenomena in laser systems. The ruby nuclear-magnetic-resonance (NMR) laser [2], among others, is an excellent test system with which to study the nature of instabilities and the routes to chaos of lasing systems. In our contribution [3] we reviewed theoretical and experimental investigations of the ruby NMR laser that operates in the rf regime and has its counterpart in the homogeneously broadened single-mode ring laser. Two topics were stressed in particular: the transition from ordered to chaotic response of the parametrically modulated laser (PML), and the transition to injection-locking of a laser with an injected signal (LIS). In both cases a control parameter of the system was slowly swept in time. For the PML it was either the amplitude or the frequency of the parametric modulation signal Apsinωpt; for the LIS it was the amplitude of the injected signal V0sinωt which was detuned by Δωa=ωa−ω from the NMR frequency ωa. In scanning the control parameter we observed in both cases sequences of instabilities leading to either regular or irregular response.

The creation of ordered structures in nonlinear many body systems far from thermal equilibrium is a subject of increasing interest. In particular, the vast field of nonlinear optics has provided many examples of systems showing the effects of cooperative behaviour. The best known is the laser where the analogy with phase transitions at thermal equilibrium was first pointed out by Graham and Haken [1] and Degiorgio and Scully [2]. A more recently discovered phenomena is optical bistability which occurs when light interacts with a nonlinear absorptive or dispersive medium inside an optical cavity [3]. In this case the systems involved exhibit a behaviour analogous to first or second order phase transitions depending on the nature of the relaxation mechanism [4].

Experiments were performed with a doubly modulated NMR laser working as a small‐signal detector. The NMR line width was modulated with a pump signal and probed with a second modulation. (AIP)

The spacing between adjacent branches in the excitation spectrum is found to increase with ħω L when magnetic effects are taken into account. Due to Zeeman splitting of the bogolon levels the energy gap Δ 2 ∞ / E F will in some cases disappear.

Experimental observations and computer simulations of the nonlinear response are discussed for a single-mode, solid-state, nuclear spin–flip, ruby nuclear-magnetic-resonance (NMR) laser. A theoretical model is derived that is based on the classical Bloch equations and that demonstrates one-to-one correspondence to a homogeneously broadened, single-mode ring laser. Experimental evidence is presented for limit cycle behavior, sequences of sub-harmonic bifurcations, transitions to chaos, noisy bands, windows of regular behavior, intermittency, abrupt transitions between different basins of attraction, and hysteresis when a physical system parameter of the NMR laser is modulated at a low frequency. First experimental results are shown for a NMR laser with an external, detuned high-frequency signal below the injection-locking threshold. In this region, the output exhibits transitions from regular to chaotic oscillations and phase-locked spiking somewhat of the nature of what has been theoretically proposed for optical systems.