Amplitude Death: The emergence of stationarity in coupled nonlinear systems

When nonlinear dynamical systems are coupled, depending on the intrinsic dynamics and the manner in which the coupling is organized, a host of novel phenomena can arise. In this context, an important emergent phenomenon is the complete suppression of oscillations, formally termed amplitude death (AD). Oscillations of the entire system cease as a consequence of the interaction, leading to stationary behavior. The fixed points that the coupling stabilizes can be the otherwise unstable fixed points of the uncoupled system or can correspond to novel stationary points. Such behaviour is of relevance in areas ranging from laser physics to the dynamics of biological systems. In this review we discuss the characteristics of the different coupling strategies and scenarios that lead to AD in a variety of different situations, and draw attention to several open issues and challenging problems for further study.Comment: Physics Reports (2012

Amplitude death phenomena in delay--coupled Hamiltonian systems

Hamiltonian systems, when coupled {\it via} time--delayed interactions, do not remain conservative. In the uncoupled system, the motion can typically be periodic, quasiperiodic or chaotic. This changes drastically when delay coupling is introduced since now attractors can be created in the phase space. In particular for sufficiently strong coupling there can be amplitude death (AD), namely the stabilization of point attractors and the cessation of oscillatory motion. The approach to the state of AD or oscillation death is also accompanied by a phase--flip in the transient dynamics. A discussion and analysis of the phenomenology is made through an application to the specific cases of harmonic as well as anharmoniccoupled oscillators, in particular the H\'enon-Heiles system.Comment: To be appeared in Phys. Rev. E (2013

The effect of finite response–time in coupled dynamical systems

The paper investigates synchronization in unidirectionally coupled dynamical systems wherein the influence of drive on response is cumulative: coupling signals are integrated over a time interval τ. A major consequence of integrative coupling is that the onset of the generalized and phase synchronization occurs at higher coupling compared to the instantaneous (τ = 0) case. The critical coupling strength at which synchronization sets in is found to increase with τ. The systems explored are the chaotic Rössler and limit cycle (the Landau–Stuart model) oscillators. For coupled Rössler oscillators the region of generalized synchrony in the phase space is intercepted by an asynchronous region which corresponds to anomalous generalized synchronization

Synthesis of Al and Ag nanoparticles through ultra-sonic dissociation of thermal evaporation deposited thin films for promising clinical applications as polymer nanocomposite

Nanoparticles (NPs) having well-defined shape, size and clean surface serve as ideal model system to investigate surface/interfacial reactions. Ag and Al NPs are receiving great interest due to their wide applications in bio-medical field, aerospace and space technology as combustible additives in propellants and hydrogen generation. Hence, in this study, we have synthesized Ag and Al NPs using an innovative approach of ultra-sonic dissociation of thin films. Phase and particle size distributions of the Ag and Al NPs have been determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thin film dissociation/dissolution mechanism, hence conversion into NPs has been characterized by SEM- scanning electron microscope. EDXA & ICPMS have been performed for chemical analysis of NPs. Optical properties have been characterized by UV-Vis and PL spectroscopy. These NPs have also been investigated for their anti-bacterial activity against Escherichia coli bacteria. To the best of our knowledge, this is the first time when NPs has been synthesized by ultra-sonic dissociation of thin films. As an application, these NPs were used further for synthesis of nanocomposite polymer membranes, which show excellent activity against bio film formation

The Gathering--Tiger, Rice, Orange, Fish

"The Gathering" is a four-channel video installation where each channel represents one of four subjects (Tiger, Rice, Orange, and Fish) respectively from left to right in a horizontal format. Language, interpersonal relationships, materiality, polyphony, and system are my key concerns in this project. I used appropriated and fragmented text for the Tiger and Fish channels, and original video footage for the Rice and Orange. The audience is invited to discover poetic syntax in the simultaneous text and image sequences. Eight digital video stills accompany the thesis

Dynamical effects of integrative time-delay coupling

We study coupled dynamical systems wherein the influence of one system on the other is cumulative: coupling signals are integrated over a time interval Τ. A major consequence of integrative coupling is that amplitude death occurs over a wider range and in a single region in parameter space. For coupled limit cycle oscillators (the Landau-Stuart model) we obtain an analytic estimate for the boundary of this region while for coupled chaotic Lorenz oscillators numerical results are presented. For given Τ we find that there is a critical coupling strength at which the frequency of oscillations changes discontinuously

A COMPARATIVE STUDY ON QUANTITATIVE ESTIMATION OF TANNINS IN TERMINALIA CHEBULA, TERMINALIA BELERICA, TERMINALIA ARJUNA AND SARACA INDICA USING SPECTROPHOTOMETER

Ashoka,  arjuna  baheda  and  harde  are  constituents  of  digestive  churna  from  old  age civilization. These drugs principally contain tannins which are widespread in plant kingdom. It is a poly-phenolic compound which is proven as antioxidants and possesses a chemo- protective potential. They are found in leaves, flowers, fruits and bark. The aim of study is to estimate the amount of tannins present in these drugs using folin-denis method.Terminalia chebula (combretaceae) (harde),    Terminalia  belerica (combretaceae)(bahera), Terminalia  arjuna (combretaceae)(arjuna)  and  Saraca indica (leguminaseae) (ashoka)  were crushed to coarse powder. The alcoholic extracts of the drugs were prepared for photometric determination of tannins using folin-denis method. The tannin concentration was determined by  the  standard  graph  of  tannic  acid  solution  and  was  found  to  be  99.55456mg/gm,9.95568mg/gm, 54.96288mg/gm, and 57.4869 mg/gm for harde, arjuna, baheda and ashoka respectively.  The concentration curve for tannic acid was determined and the correlation coefficient was calculated and was found to be 0.998 which indicates the good linearity between the concentration and the absorbance. It has been found that the tannins form the stable complexes with protein, starch and metal chelates by disturbing the metabolic activity of the bacterial enzymes nutrient availability, and functionality of biological membranes. The present study can be used as one of the parameters for standardization of medicinal plants. Â

A cross-sectional study to evaluate the cranial magnetic resonance imaging findings in eclampsia and severe pre-eclampsia patients and its clinical correlation

Background: Pre-eclampsia/eclampsia remains a high contributor towards maternal mortality and morbidity and also the poor perinatal outcome. Thus, timely prediction of the onset of eclampsia and starting appropriate treatment as early as possible is important for favourable maternal and perinatal outcome. However, there is a dearth of studies, especially in the Indian scenario which correlates the severity of pre-eclampsia/eclampsia and the cranial magnetic resonance imaging (MRI) findings, therefore, this study was planned to fill the lacuna. Material and Methods: A total of forty patients admitted in the department, of forty, twenty patients were diagnosed with eclampsia and twenty patients with severe pre-eclampsia. MRI was performed in all these 40 patients and they were divided into two groups. Group I (MRI findings positive n = 17) and Group II (MRI findings negative n = 23), the patients once had agreed to (with consent) were sent to MRI centre for MRI to be performed. All the data required along with the patients' sign and symptom were recorded in the pro foma designed for this study. Results: The difference in the study groups was statistically significant regarding headache, seizures, depression of consciousness and visual disorder (P = 0.0085, <0.0001, <0.0001, and <0.0001, respectively). In MRI positive findings patients, the occipital cortex was involved in 100% of patients, parietal cortex in 58.82%, frontal cortex in 58.82% and temporal cortex in only 11.77% of patients. Basal ganglia had an infarct in 11.77%. Conclusion: We have observed patients suffering from severe pre-eclampsia and having positive cerebral findings on MRI scan, However employing MRI for screening is not cost-effective and large-scale randomised control trials are needed to further confirm the role of MRI in severe pre-eclampsia