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61.
We show that firing activity (spiking) can be regularized by noise in a FitzHugh-Nagumo (FHN) neuron model when operating slightly beyond the supercritical Hopf bifurcation (in the "canard" region). We also provide the conditions for imperfect phase locking between interspike intervals and low amplitude quasiharmonic oscillations. For the imperfect phase locking no need exists of an external signal as it follows from the FHN intrinsic dynamics. 相似文献
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S. Balestra S. Cecchini M. Cozzi M. Errico F. Fabbri G. Giacomelli R. Giacomelli M. Giorgini A. Kumar S. Manzoor J. McDonald G. Mandrioli S. Marcellini A. Margiotta E. Medinaceli L. Patrizii J. Pinfold V. Popa I.E. Qureshi O. Saavedra Z. Sahnoun G. Sirri M. Spurio V. Togo A. Velarde A. Zanini 《The European Physical Journal C - Particles and Fields》2008,55(1):57-63
The SLIM experiment was a large array of nuclear track detectors located at the Chacaltaya high altitude Laboratory (5230 m
a.s.l.). The detector was in particular sensitive to intermediate mass magnetic monopoles, with masses 105 GeV <MM< 1012 GeV. From the analysis of the full detector exposed for more than 4 years a flux upper limit of 1.3×10-15 cm-2 s-1 sr-1 for downgoing fast intermediate mass monopoles was established at the 90% C.L.
PACS 14.80.Hv; 29.40.Wk; 29.90.+r 相似文献
64.
Hilles H Maestro A Monroy F Ortega F Rubio RG Velarde MG 《The Journal of chemical physics》2007,126(12):124904
The equilibrium properties of monolayers of two polymers: poly(octadecyl acrylate) and poly(vinyl stearate) on water have been measured. The surface pressure (Pi) versus surface concentration (Gamma) curves indicate that the water-air interface is a poor solvent for both polymers. The thermal expansivity shows a sharp change near room temperature. This behavior is typical of a glass transition; this is the first time that such a plot is observed for Langmuir films. The Pi vs Gamma curves measured by the continuous compression method show strong anisotropy effects. They also show that the monolayer is brought into nonequilibrium states depending on the compression rate. Within the linear regime, the relaxation experiments were bimodal. The longest relaxation time strongly increases as T is decreased, which might be compatible with the high increase of viscosity in the glass transition. The oscillatory barrier experiments showed that the maximum strain of the linear regime is smaller than 3% for both monolayers. The Fourier-transform analysis of the oscillatory experiments beyond the linear regime points out the contribution of different harmonics in the response function. Oscillations in the nonlinear regime show hysteresis cycles. The results obtained indicate that some of the previously published data for these polymer monolayers correspond to nonequilibrium states. 相似文献
65.
Biochar is a nanoengineered sorbent proposed to control the contamination derived from the presence of residual concentrations of sulfonamides in soil. In this work, we evaluated the sorption of sulfanilamide (SFA) in commercial biochar (BC) produced at 500 °C from oak hardwood (Quercus ilex) and its analog activated with 2% (w/w) Fe (BC-Fe). Subsequently, the effect on dissipation and transport of SFA in untreated soil and soil treated with BC and BC-Fe was also assessed. Laboratory batch studies revealed that BC-Fe increased the sorption of SFA as compared to the pristine BC with Kd of 278 and 98 L/kg, respectively. The dissipation of SFA in either untreated soil or soil treated with BC or BC-Fe was similar, displaying half-lives ranging between 4 and 6.4 days. Conversely, the concurrent determination of sorption during the incubation experiment showed that lower amounts of SFA in solution at the beginning of the experiments were bioavailable in BC-Fe-treated soil when compared to the rest of the treatments shortly after application. Leaching column studies confirmed the amendment’s capability to bind the SFA compound. Therefore, the decrease in bioavailability and movement of SFA in treated soils suggest that biochar soil application can reduce SFA soil and water contamination. According to our results, BC surface modification after Fe activation may be more appropriate for water decontamination than for soil since there were no significant differences between the two types of biochar when added to the soil. Therefore, these outcomes should be considered to optimize the SFA mitigation potential of biochar. 相似文献
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Larue J Schäfer T Matsiev D Velarde L Nahler NH Auerbach DJ Wodtke AM 《Physical chemistry chemical physics : PCCP》2011,13(1):97-99
We report the first direct measurement of the kinetic energy of exoelectrons produced by collisions of vibrationally excited molecules with a low work function metal surface exhibiting electron excitations of 64% (most probable) and 95% (maximum) of the initial vibrational energy. This remarkable efficiency for vibrational-to-electronic energy transfer is in good agreement with previous results suggesting the coupling of multiple vibrational quanta to a single electron. 相似文献
68.
Substantial progress has been made in the quantitative understanding and interpretation of the hydrogen bonding and ordering structure of the air/water interface since the first sum-frequency generation vibrational spectroscopy (SFG-VS) measurement by Q. Du et al. in 1993 (Phys. Rev. Lett. 1993, 70, 2312-2316). However, there are still disagreements and controversies on the consistency between the different experimental measurements, as well as in the theoretical and computational results. One critical problem lies in the lack of consistency between the SFG-VS intensity measurements and the recently developed SFG-VS phase spectra measurements of the neat air/water interface, which has inspired various theoretical efforts. In this report, the reliability of the SFG-VS intensity spectra of the air/neat water interface is to be quantitatively examined, and possible sources of inaccuracies in the SFG-VS phase spectral measurement are to be discussed based on the nonresonant SHG phase measurements. Solid evidence is shown indicating that the SFG-VS intensity spectra from different laboratories are now quantitatively converging and in agreement with each other. However, the possible inaccuracies and inconsistencies in the SFG-VS phase spectra measurements need to be carefully examined against a properly corrected phase standard to take full advantage of this powerful experimental tool. 相似文献
69.
70.
M. G. Velarde L. Brizhik A. P. Chetverikov L. Cruzeiro W. Ebeling G. Röpke 《International journal of quantum chemistry》2012,112(13):2591-2598
In this study, it is shown that two added, excess electrons with opposite spins in one‐dimensional crystal lattices with quartic anharmonicity may form a bisolectron, which is a localized bound state of the paired electrons to a soliton‐like lattice deformation. It is also shown that when the Coulomb repulsion is included, the wave function of the bisolectron has two maxima, and such a state is stable in lattices with strong enough electron (phonon/soliton)–lattice coupling. Furthermore, the energy of the bisolectron is shown to be lower than the energy of the state with two separate, independent electrons, as even with account of the Coulomb repulsion the bisolectron binding energy is positive. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献