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We use tools of the equilibrium statistical mechanics of disordered systems to study analytically the statistical properties of an ecosystem composed of N species interacting via random mutual interactions, as well as via deterministic self-interactions of order p>/=2. We show that the main effect of increasing the order of the interactions among the species is to make the system less competitive, in the sense that the fraction of extinct species is greatly reduced. In addition, we find that for p>2 there is a threshold value which gives a lower bound to the concentration of the surviving species, preventing then the existence of rare species and, consequently, increasing the robustness of the ecosystem to external perturbations. 相似文献
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Medvedev VV Yakshin AE van de Kruijs RW Krivtsun VM Yakunin AM Koshelev KN Bijkerk F 《Optics letters》2012,37(7):1169-1171
An extreme ultraviolet multilayer mirror with an integrated spectral filter for the IR range is presented and experimentally evaluated. The system consists of an IR-transparent B4C/Si multilayer stack which is used both as EUV-reflective coating and as a phase shift layer of the resonant IR antireflective (AR) coating. The AR coating is optimized in our particular case to suppress CO2 laser radiation at a wavelength of 10.6 μm, and a suppression of more than two orders of magnitude is demonstrated. The method allows high suppression over a large angular acceptance range, relevant for application in lithography systems. 相似文献
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We solve the thermoelastic problem for a plane with a rectilinear heat-conducting crack whose conductivity depends on its opening. By modeling the crack as a thin inclusion of variable thickness we reduce the problem to a system of singular integrodifferential equations for the potential densities of the temperature field. We study the behavior of the unknown functions at the ends of the contour of integration and, using a numerical-iteration method, we also determine the solution of the problem. We find an approximate asymptotic solution in the case of a weakly conducting crack.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 31, 1990, pp. 54–58. 相似文献
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Allison M Fox Mike Anderson Corinne Reid Tim Smith Dorothy VM Bishop 《BMC neuroscience》2010,11(1):1-15
Background
We examined development of auditory temporal integration and inhibition by assessing electrophysiological responses to tone pairs separated by interstimulus intervals (ISIs) of 25, 50, 100, 200, 400, and 800 ms in 28 children aged 7 to 9 years, and 15 adults.Results
In adults a distinct neural response was elicited to tones presented at ISIs of 25 ms or longer, whereas in children this was only seen in response to tones presented at ISIs above 100 ms. In adults, late N1 amplitude was larger for the second tone of the tone pair when separated by ISIs as short as 100 ms, consistent with the perceptual integration of successive stimuli within the temporal window of integration. In contrast, children showed enhanced negativity only when tone pairs were separated by ISIs of 200 ms. In children, the amplitude of the P1 component was attenuated at ISIs below 200 ms, consistent with a refractory process.Conclusions
These results indicate that adults integrate sequential auditory information into smaller temporal segments than children. These results suggest that there are marked maturational changes from childhood to adulthood in the perceptual processes underpinning the grouping of incoming auditory sensory information, and that electrophysiological measures provide a sensitive, non-invasive method allowing further examination of these changes. 相似文献7.
P. Porytsky I. Krivtsun V. Demchenko U. Reisgen O. Mokrov A. Zabirov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,57(1):77-85
The application of the Lorentzian plasma theory for the calculation of the properties of multicomponent electric arc plasma
is considered. It is shown that this model gives satisfactory results in the temperature range, which is corresponding to
the weakly ionized arc plasma and arc plasma with dominant first ionization. The calculations are provided for the arc plasmas
of noble gases and their mixtures between them and also that with metals. It is also pointed that the discrepancy between
the electron temperature and gas temperature can be significant even at relatively weak electric fields, that fact must be
taken into account under the simulation of arc discharges. 相似文献
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Wangler M Roth DA Krivtsun VM Pak I Winnewisser G Geleijns M Wormer PE van der Avoird A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(11):2499-2504
The spectrum of the weakly bound complex Ar-CH4 in the 7 microm region was discovered, analysed, and compared with a spectrum, predicted from ab initio calculations. The measurements were made by probing a supersonic gas expansion with a tunable diode laser (TDL). Several bands of Ar-CH4 associated with different ro-vibrational transitions of the v4 vibration of CH4 were recorded and analysed in a spectral region from 1295 to 1330 cm(-1). In particular the following transitions were studied: j = 1 <-- 0 (at 1311 cm(-1)) reported in Pak et al. [Z. Naturforsch. 53 (1998) 725], j = 0 <-- 1 (at 1301 cm(-1)), j = 2 <-- 1 (at 1316 cm(-1)), and j = 3 <-- 2 transitions (at 1322 cm(-1)). Here, j denotes the angular momentum of the methane unit inside the complex. Analysis of the recently recorded j = 1 <-- 1 transitions at about 1306 cm(-1) in the region of methane Q(1) is in progress. The experimental results are compared with ab initio calculations. The close agreement between observed and ab initio spectra is convincingly demonstrated with respect to the gross spectral features, including many details of the spectra. 相似文献
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Medvedev VV Yakshin AE van de Kruijs RW Krivtsun VM Yakunin AM Koshelev KN Bijkerk F 《Optics letters》2011,36(17):3344-3346
We have developed a multilayer mirror for extreme UV (EUV) radiation (13.5?nm), which has near-zero reflectance for IR line radiation (10.6?μm). The EUV reflecting multilayer is based on alternating B4C and Si layers. Substantial transparency of these materials with respect to the IR radiation allowed the integration of the multilayer coating in a resonant quarter-wave structure for 10.6?μm. Samples were manufactured using magnetron sputtering deposition technique and demonstrated suppression of the IR radiation by up to 3 orders of magnitude. The EUV peak reflectance amounts 45% at 13.5?nm, with a bandwidth at FWHM being 0.284?nm. Therefore such a mirror could replace conventional multilayer mirrors to suppress undesired spectral components in monochromatic imaging applications, including EUV photolithography. 相似文献