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Pfeuty B.,CNRS Atomic and Molecular Physics Laboratory
Development (Cambridge) | Year: 2015

Proper tissue development requiresthat stem/progenitor cells precisely coordinate cell division and differentiation in space and time. Notch-Hes1 intercellular signaling, which affects both differentiation and cell cycle progression and directs cell fate decisions at various developmental stages in many cell types, is central to this process. This study explored whether the pattern of connections among the cell cycle regulatory module, the Notch effector Hes1 and the proneural factor Ngn2 could explain salient aspects of cell fate determination in neural progenitors. A mathematical model that includes mutual interactions between Hes1, Ngn2 and G1-phase regulators was constructed and simulated at the single- and two-cell levels. By differentially regulating G1-phase progression, Hes1 and Ngn2 are shown to induce two contrasting cell cycle arrest states in early and late G1, respectively. Indeed, steady Hes1 overexpression promotes reversible quiescence by downregulating activators of G0/G1 exit and Ngn2. Ngn2 also downregulates activators of G0/G1 exit, but cooperates with Cip/Kip proteins to prevent G1/S transit, whereby it promotes G1-phase lengthening and, ultimately, contributes to reinforcing an irreversible late G1 arrest coincident with terminal differentiation. In this scheme, Hes1 oscillation in single cells is able to maintain a labile proliferation state in dynamic balance with two competing cell fate outputs associated with Hes1-mediated and Ngn2-mediated cell cycle arrest states. In Delta/Notch-connected cells, Hes1 oscillations and a lateral inhibition mechanism combine to establish heterogeneous Hes1, Ngn2 and cell cycle dynamics between proliferating neural progenitors, thereby increasing the chances of asymmetric cell fate decisions and improving the reliability of commitment to differentiation. © 2015. Published by The Company of Biologists Ltd. Source

Conforti M.,CNRS Atomic and Molecular Physics Laboratory | Conforti M.,University of Brescia
Optics Letters | Year: 2014

The evolution of light pulses and beams in a quasi-phase-matched (QPM) quadratic medium is usually described by considering only the spatial harmonic of the QPM grating that minimizes the residual phase-mismatch. I show that, for strongly phase-mismatched interactions (the cascading regime), several harmonics need to be accounted for in order to obtain the correct value of the effective cubic nonlinearity, for which I find a simple analytical expression. I discuss the effects of the higher order harmonics of the grating on solitary wave propagation. © 2014 Optical Society of America. Source

Jaimes-Reategui R.,University of Guadalajara | Sevilla-Escoboza R.,University of Guadalajara | Huerta-Cuellar G.,University of Guadalajara | Taki M.,CNRS Atomic and Molecular Physics Laboratory
Physical Review Letters | Year: 2011

Clear evidence of rogue waves in a multistable system is revealed by experiments with an erbium-doped fiber laser driven by harmonic pump modulation. The mechanism for the rogue wave formation lies in the interplay of stochastic processes with multistable deterministic dynamics. Low-frequency noise applied to a diode pump current induces rare jumps to coexisting subharmonic states with high-amplitude pulses perceived as rogue waves. The probability of these events depends on the noise filtered frequency and grows up when the noise amplitude increases. The probability distribution of spike amplitudes confirms the rogue wave character of the observed phenomenon. The results of numerical simulations are in good agreement with experiments. © 2011 American Physical Society. Source

Constantin F.L.,CNRS Atomic and Molecular Physics Laboratory
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2015

Calculations of the sensitivities of rotational and rovibrational transitions of isotopic lithium hydride in the electronic ground state to a variation of the proton-to-electron mass ratio constant are presented. A highly enhanced sensitivity coefficient is observed for the splitting of near resonant transitions arising from a cancellation between rotational intervals and frequency shifts associated respectively to the isotope effect, to the anharmonicity and to the rotation-vibration interaction. It ranges from 73 748.47(1) to -21 672(137) for the transitions with low to intermediate rotational quantum numbers in the lowest vibrational energy levels. The splittings of rotational transitions of 7LiD in the vibrational level v = 0 and 6LiD in the vibrational level v = 2 have a sensitivity coefficient of ∼-3 for J up to 29 and that of 6LiH R(0) and 7LiH R(1) rovibrational transitions in the v = 0 - >1 band has a sensitivity coefficient of -585. The approach allowed comparison of frequency intervals between rotational lines with ammonia inversion lines detected in the microwave spectra of B0218 + 367 quasar to put constraints to a variation of the proton-to-electron mass ratio. © 2015 IOP Publishing Ltd. Source

Carvajal M.,University of Huelva | Kleiner I.,University Paris Diderot | Demaison J.,CNRS Atomic and Molecular Physics Laboratory
Astrophysical Journal, Supplement Series | Year: 2010

A compilation of the available spectroscopicmillimeter- and submillimeter-wave data of the ground and first excited states of 13C1-methyl formate (H13COOCH3) has been carried out. The exhaustive analysis of the available transition lines of H13COOCH3 has led to the assignment of 7457 spectral lines by means of a global fit of 45 parameters, using the Rho-Axis Method and the BELGI-Cs code, with a resulting unitless standard deviation of 0.57. Over 1600 lines are included for the first time in the fit. In addition, the line strengths of spectral lines are also calculated using the most recent experimental measurement of the electric dipole moment. In conclusion, the present study represents a notable improvement with respect to previous H 13COOCH3 spectral analyses. Therefore, the better accuracy of the present analysis may help the future identification of new H 13COOCH3 lines in the interstellar and circumstellar media, and may contribute to decrease some of the spectral confusion due to these species in astronomical surveys. © 2010. The American Astronomical Society. All rights reserved. Source

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