Aspects of hydrogen CARS thermometry

The temperature of hydrogen in a graphite tube furnace has been determined using broadband coherent anti-Stokes Raman scattering (CARS) spectroscopy. Significant laser-induced population changes were observed within the vibrational state manifold, whereas the rotational envelope in both fundamental and hot band remained unchanged.     

Characterization of complex networks by higher order neighborhood properties

A concept of higher order neighborhood in complex networks, introduced previously [Phys. Rev. E 73, 046101 (2006)], is systematically explored to investigate larger scale structures in complex networks. The basic idea is to consider each higher order neighborhood as a network in itself, represented by a corresponding adjacency matrix, and to settle a plenty of new parameters in order to obtain a best characterization of the whole network. Usual network indices are then used to evaluate the properties of each neighborhood. The identification of high order neighborhoods is also regarded as intermediary step towards the evaluation of global network properties, like the diameter, average shortest path between node, and network fractal dimension. Results for a large number of typical networks are presented and discussed.     

Open dynamic behaviour of financial markets

Open dynamic behaviour of financial markets with internal interactions between agents and with external “fields” from other systems are investigated using the approach of Grossman and Stiglitz for inefficient markets, and Keynes for interference of the market using physics of finance (referred to hereafter as phynance). The simulation results indicate that the NYSE data analyzed in Plerou, V. et al., Nature 421, 130 (2003) can be fitted by an equation of order parameter Φ and local deviation R of type: -(R+0.03) Φ+ 0.6 Φ³ + 0.02 = 0, which is shown to be in remarkable agreement with Plerou's data.     

Correlations in financial time series: established versus emerging markets

Long-time correlations in both well-developed and emerging market indexes are studied. The Hurst exponent as well as detrended fluctuations analysis (DFA) are used as technical tools. Some features that seem to be specific for developing markets are discovered and briefly discussed. Received 17 October 2000     

Lévy-type complex diameter modulation in semiconductor nanowire growth

We have observed a non-periodic diameter modulation in SiC nanowire growth. The modulation was tentatively attributed to a stick-slip motion in a self-organized vapor-liquid-solid (VLS) growth, and was characterized by methods of time-series analysis. From the power-law decay behavior of a fat tail of the probability distribution of increments with the exponent 2.1±0.2, the modulation was interpreted as a Lévy flight. The degree of determinism is also discussed.     

The application of CARS for temperature measurements in high pressure combustion systems

The determination of accurate temperatures from CARS N₂ Q-branch spectra in premixed flames is discussed for pressures up to 40 bar. The influence of collisional line narrowing in the CARS spectra is modelled by a MEG fitting law. It takes into account collisions of N₂ with CO₂ and H₂O. The analysis of the CARS data showed that the non-resonant background has an increasing influence on temperature with increasing pressure. Little influence on the quality of the fit between theory and experiment was found. Since there is a danger of residual systematic temperature deviations, which cannot be identified from the quality of the fit, spontaneous rotational Raman scattering is employed as an independent measuring technique.     

Influence of nonlinear quantum dissipation on the dynamical properties of the f-deformed Jaynes-Cummings model in the dispersive limit

We investigate the effect of a static electric field on photoionization of the He atom in the ground 1S and low-lying 2S and 2P excited states. The field-affected ionization potential and photoionization cross-section are determined from the complex eigenvalues of the time-dependent Schr?dinger equation solved by the complex rotation method in the Floquet ansatz. Accuracy of the method is enhanced by the use of the Hylleraas basis set. For the ground state of helium, we find that the total photoionization cross-section remains constant or decreases as a function of the DC field strength until this field reaches a certain critical value. For the low-lying excited states, effect of the static field is similar to the ordinary DC Stark effect.     

Planar imaging of a laboratory flame and of internal combustion in an automobile engine using UV rayleigh and fluorescence light

Rayleigh scattering of tunable excimer laser light (193 nm and 248 nm) is used to obtain 2-D images of the distribution of total densities in a laboratory flame and in a cylinder of an automobile engine. Because the UV light is very strongly scattered, there is ample signal and there is excellent contrast of Rayleigh light against surface scattered light, even in the small volume of the engine cylinder. The laboratory flame data are converted to an image of the temperature field. The Rayleigh images are compared with those from planar laser induced predissociative fluorescence, which yield state-specific densities of selected molecules. The experimental arrangement is the same except for the selection of laser wavelength and the filtering of the radiated light.     

Ion pump as molecular ratchet and effects of noise: electric activation of cation pumping by Na,K-ATPase

Na,K-ATPase is a universal ion pump of the biological cell. Under physiological conditions, it uses the γ-phosphorus bond energy of ATP during hydrolysis to pump 2 K⁺ inward and 3 Na⁺ outward; both being uphill transports. The experiment presented here demonstrates that the protein transporter can also use electric energy to fuel its pump activity. A theory of electroconformational coupling (TEC) is described and an experiment performed to verify several predictions of the model. Analysis based on the TEC model suggests that Na,K-ATPase is a Brownian ratchet. The enzyme harvests energy from the applied field by means of the field-induced conformational oscillation or fluctuation. However, high efficiency of energy transduction can only be achieved with an electric field of certain intensities, frequencies and waveforms. This property of the enzyme allows us to define an electric signal and differentiate it from electric noise on the basis of the analysis by the TEC model. Data show that electric noise alone does not induce pump activity. However, an appropriate power level of noise imposed on a signal can enhance the pump efficiency. The effect of noise on the signal transduction of Na,K-ATPase is reminiscent of the stochastic resonance phenomenon reported in other biological systems [3, 35]. The TEC model embodies many common features of enzymes and biological motors. It is potentially energy-efficient, much more so than models based on the ion-rectification mechanism. Received: 1 November 2001 / Accepted: 5 March 2002 / Published online: 22 April 2002     

Multi-species detection in spray flames with tunable excimer lasers

Planar imaging with tunable excimer-laser sheet illumination is used to determine spatial distributions of different species in liquid-fuelled spray flames of commercial oil burning furnaces. Two burner configurations, which differ only in the fuel/air mixing devices, are investigated to understand why one configuration yields 30% less NO_x emission. Iso-octane and n-heptane fuels are used. To understand the origin for NO_x reduction spatial distributions of reactants (fuel, O₂), the reaction intermediate OH and the pollutant NO are recorded. OH and O₂ are measured by LIPF, NO by LIF. Fuel distributions are determined by another broad-band emission, whose origin is not yet identified. Both single shot and averaged distributions are recorded. The averaged distributions are extremely reproducible and depend sensitively on details of the burner geometry and the fuel/air mixing device. They can clearly be used to distinguish fine details in different injection systems. The spatial distribution of different species relative to each other yield considerable insight in the differences between the two combustion processes. On the basis of purely qualitative visualization it is possible to understand the origin for NO_x reduction: it results from faster injection of air in the one fuel/air mixing device.