Cristina Stan

Analysis of the intermittent behavior in a low-temperature discharge plasma by recurrence plot quantification

The paper presents applications of the recurrence plot quantification to the analysis of type 1 intermittency observed in a discharge plasma. The main measures of recurrence plot analysis considered are the laminarity and the determinism. First, it is demonstrated that the laminarity measure can be related to the average time between chaotic bursts in this type of intermittency. Second, it is shown that the determinism measure introduced by the recurrence plot quantification depends on the control parameter as a decreasing exponential. The test of the results is performed by analyzing the determinism measure for type 1 intermittency observed in the logistic map. It is also shown that the role of the intrinsic noise of the plasma can easily be identified by this technique.

Investigation on series of length of coding and non-coding DNA sequences of bacteria using multifractal detrended cross-correlation analysis

In the framework of multifractal detrended cross-correlation analysis, we investigate characteristics of series of length of coding and non-coding DNA sequences of some bacteria and archaea. We propose the use of a multifractal cross-correlation series that can be defined for any pair of equal lengths data sequences (or time series) and that can be characterized by the full set of parameters that are attributed to any time series. Comparison between characteristics of series of length of coding and non-coding DNA sequences and of their associated multifractal cross-correlation series for selected groups is used for the identification of class affiliation of certain bacteria and archaea. The analysis is carried out using the dependence of the generalized Hurst exponent on the size of fluctuations, the shape of the singularity spectra, the shape and relative disposition of the curves of the singular measures scaling exponent and the values of the associated parameters. Empirically, we demonstrate that the series of lengths of coding and non-coding sequences as well as the associated multifractal cross-correlation series can be approximated as universal multifractals.

Gravity and cantorian space-time

Abstract Within the weak field approximation, based on the hypothesis of the superconducting properties of cosmic dust and on fact that the gravitomagnetic field ‘grafts’ a kind of quasi crystal on ‘space’, and holds the so created structure by ‘pinning’ effect, it is argued that space-time may be indeed Cantorian as suggested by El Naschie. In this context the relation between gravitation and ‘composite fermionizing’ mechanism offers a new interpretation of the supplemental precession of the ecliptic tilt as a property of this space.

Similarity analysis for DNA sequences based on chaos game representation. Case study: the albumin.

Using chaos game representation we introduce a novel and straightforward method for identifying similarities/dissimilarities between DNA sequences of the same type, from different organisms. A matrix is associated to each CGR pattern and the similarities result from the comparison between the matrices of the sequences of interest. Three different methods of analysis of the resulting difference matrix are considered: a 3-dimensional representation giving both local and global information, a numerical characterization by defining an n-letter word similarity measure and a statistical evaluation. The method is illustrated by implementation to the study of albumin nucleotides sequences from eight mammal species taking as reference the human albumin.

Modelling of the Temporal Behaviour of the Inter-Anode Current in a System of Two Coupled Electrical Discharges

We present an experimental study on the dynamics of space charge configurations taking place in the inter-anode space of two electrical glow discharges coupled by a dc biasing voltage of one discharge with respect to the other one in the presence of a small periodic signal. Modelling the system as two coupled perturbed Van der Pol oscillators, we investigate the influence of the coupling strength on the global dynamic response and compare it with experimental data. We find good agreement between the experimental data and the computation results for the following types of analysis: time series, spectra, phase portraits, Lyapunov exponents and correlation dimensions.

The uncertainty relation for an assembly of Planck-type oscillators. A possible GR-quantum mechanics connection

Abstract It is shown that an assembly of Planck-type oscillators may be described by a continuous group with three parameters. In such a case, the uncertainty relation may be obtained by the application of a theorem on the invariant functions, when a simultaneous action of two isomorphic groups is involved. The groups parameters are interpreted by means of a variational principle, as field amplitudes of a stationary metric, while the groups invariant function is interpreted as the square root of a wave function satisfying a Schrodinger-type equation.

Gravitational paramagnetism, diamagnetism and gravitational superconductivity

In the weak field approximation to the gravitational field equations, we study gravitational paramagnetism and diamagnetism, the gravitational Meissner effect and gravitational superconductivity. The spontaneous symmetry breaking corresponds to crossing from closed geodesics to open ones, and to the existence of a critical temperature in the frame of a gauge model at finite temperature. In this later case one can obtain expressions giving the dependence of several superconducting parameters on temperature.

Dynamic behavior of a nematic liquid crystal mixed with CoFe2O4 ferromagnetic nanoparticles in a magnetic field

The dynamic behavior of a mixture of 4-cyano-4′-pentylbiphenyl (5CB) with 1% CoFe2O4 nanoparticles was analyzed. Experimental data indicate a high stability of the nematic director in the mixture compared to a reference 5CB sample in the magnetic field. The ferrite nanoparticles agglomerate forming long chains as observed in polarized microscopy images. These chains have a very high influence on the magneto-optic effect of the cell. When the magnetic field is applied on the mixture, the chains tend to align with the field direction but, due to their large size, they remain oriented obliquely between the support plates. Thus, the nematic molecules anchored on their surface can not reorient with the field and only a small distortion angle of the liquid crystal molecular director is observed. A comparison with a previously developed theoretical model confirms this small deviation.

Effect of Gramicidin S on the Dipalmitoylphosphatidyl- glycerol Thermotropic Phase Transition in DPPG/GS Systems: A Mathematical Approach

We present a mathematical approach to the experimental data recorded via Fourier transform–infrared spectroscopy regarding the influence of the concentration of the antimicrobial peptide gramicidin S (GS) on the thermotropic phase transition of the dipalmitoylphosphatidyl-glycerol (DPPG) lipid bilayer membrane in DPPG/GS systems. The model is based on the influence of the GS concentration on the parameters of a nonlinear damped oscillator, which models the CH2 symmetric stretching band.

Dynamics of the plasma of a twin discharge system induced by external perturbations

In this work we present new results on the dynamics of charge structures generated in the inter-anode space of a twin electric discharge system both for free running and for sinusoidal forcing. We study the change of plasma dynamics as function of the amplitude of the ac forcing for two dc biasing values. In a certain range of the control parameter, proportional to the amplitude of the sinusoidal perturbation, the dynamics can be dramatically changed. The results of the computational model proposed in previous works for the system are in reasonable agreement with the experiment.