Okra peel-derived nitrogen-doped carbon dots: Eco-friendly synthesis and multi-functional applications in heavy metal ion sensing, nitro compound detection and environmental remediation.

The present study explores the kitchen waste okra peels derived synthesis of nitrogen doped carbon dots (N-CDs) via simple carbonization followed by reflux method. The synthesized N-CDs was characterized using, TEM, XPS, FTIR, XRD, Raman, UV-Visible and Fluorescence Spectroscopy. The N-CDs emits bright blue emission at 420 nm with 12 % of quantum yield as well as it follows excitation dependent emission.

Spatiotemporal patterns corresponding to phase synchronization and generalized synchronization states of thermoacoustic instability.

Thermoacoustic instability in turbulent combustion systems emerges from the complex interplay among the flame, flow, and acoustic subsystems. While the onset of thermoacoustic instability exhibits a global order, the characteristics of local interactions between subsystems responsible for this order are not well understood. Here, we utilize the framework of synchronization to elucidate the spatiotemporal interactions among heat release rate fluctuations in the flame, velocity fluctuations in the flow, and acoustic pressure fluctuations in a turbulent combustor, across the bluff-body stabilized flame.

Facile synthesis of sulphur-doped carbon dots (S-CDs) using a hydrothermal method for the selective sensing of Cr and Fe ions: application to environmental water sample analysis.

In this work, we used a one-step hydrothermal method to synthesize blue-emission sulfur-doped carbon dots (S-CDs) using jaggery as a carbon precursor. The synthesized carbon quantum dots showed low toxicity, good water solubility, anti-interference properties, and stable fluorescence. When excited at 310 nm, the S-CDs produced bright emission with a quantum yield of 7.

Mitigation of limit cycle oscillations in a turbulent thermoacoustic system via delayed acoustic self-feedback.

We report the occurrence of amplitude death (AD) of limit cycle oscillations in a bluff body stabilized turbulent combustor through delayed acoustic self-feedback. Such feedback control is achieved by coupling the acoustic field of the combustor to itself through a single coupling tube attached near the anti-node position of the acoustic standing wave. We observe that the amplitude and dominant frequency of the limit cycle oscillations gradually decrease as the length of the coupling tube is increased.

Rijke tube: A nonlinear oscillator.

Dynamical systems theory has emerged as an interdisciplinary area of research to characterize the complex dynamical transitions in real-world systems. Various nonlinear dynamical phenomena and bifurcations have been discovered over the decades using different reduced-order models of oscillators. Different measures and methodologies have been developed theoretically to detect, control, or suppress the nonlinear oscillations.

Dynamical states and bifurcations in coupled thermoacoustic oscillators.

The emergence of rich dynamical phenomena in coupled self-sustained oscillators, primarily synchronization and amplitude death, has attracted considerable interest in several fields of science and engineering. Here, we present a comprehensive theoretical study on the manifestation of these exquisite phenomena in a reduced-order model of two coupled Rijke tube oscillators, which are prototypical thermoacoustic oscillators. We characterize the dynamical behaviors of two such identical and non-identical oscillators by varying both system parameters (such as the uncoupled amplitudes and the natural frequencies of the oscillators) and coupling parameters (such as the coupling strength and the coupling delay).

Anticipating synchrony in dynamical systems using information theory.

Synchronization in coupled dynamical systems has been a well-known phenomenon in the field of nonlinear dynamics for a long time. This phenomenon has been investigated extensively both analytically and experimentally. Although synchronization is observed in different areas of our real life, in some cases, this phenomenon is harmful; consequently, an early warning of synchronization becomes an unavoidable requirement.

Sawmill waste derived carbon dots as a fluorescent probe for synthetic dyes in soft drinks.

Herein, for the first time the carbon dots (CDs) were synthesized by reflux method from sawmill waste material. We also represent a novel strategy based on fluorescent CDs for determination of ponceau 4R and allura red dyes in soft drinks. Interestingly, both the dyes were sensitive and showed effective fluorescence quenching of the CDs owing to the interaction between them.

Experimental investigation on the susceptibility of minimal networks to a change in topology and number of oscillators.

Understanding the global dynamical behavior of a network of coupled oscillators has been a topic of immense research in many fields of science and engineering. Various factors govern the resulting dynamical behavior of such networks, including the number of oscillators and their coupling schemes. Although these factors are seldom significant in large populations, a small change in them can drastically affect the global behavior in small populations.

Bursting during intermittency route to thermoacoustic instability: Effects of slow-fast dynamics.

Intermittency observed prior to thermoacoustic instability is characterized by the occurrence of bursts of high-amplitude periodic oscillations (active state) amidst epochs of low-amplitude aperiodic fluctuations (rest state). Several model-based studies conjectured that bursting arises due to the underlying turbulence in the system. However, such intermittent bursts occur even in laminar and low-turbulence combustors, which cannot be explained by models based on turbulence.

Recurrence analysis of slow-fast systems.

Many complex systems exhibit periodic oscillations comprising slow-fast timescales. In such slow-fast systems, the slow and fast timescales compete to determine the dynamics. In this study, we perform a recurrence analysis on simulated signals from paradigmatic model systems as well as signals obtained from experiments, each of which exhibit slow-fast oscillations.

Synchronization route to weak chimera in four candle-flame oscillators.

Synchronization and chimera are examples of collective behavior observed in an ensemble of coupled nonlinear oscillators. Recent studies have focused on their discovery in systems with least possible number of oscillators. Here we present an experimental study revealing the synchronization route to weak chimera via quenching, clustering, and chimera states in a single system of four coupled candle-flame oscillators.

Dynamical systems approach to study thermoacoustic transitions in a liquid rocket combustor.

Liquid rockets are prone to large amplitude oscillations, commonly referred to as thermoacoustic instability. This phenomenon causes unavoidable developmental setbacks and poses a stern challenge to accomplish the mission objectives. Thermoacoustic instability arises due to the nonlinear interaction between the acoustic and the reactive flow subsystems in the combustion chamber.

Oscillation quenching and phase-flip bifurcation in coupled thermoacoustic systems.

Oscillatory instabilities, although ubiquitous in nature, are undesirable in many situations such as biological systems, swaying of bridges and skyscrapers, aero-acoustic flutter, prey-predator and disease spread models, and thermoacoustic systems, where they exhibit large amplitude periodic oscillations. In the present study, we aim to study the suppression mechanism of such undesired oscillations in a pair of thermoacoustic oscillators, also known as horizontal Rijke tubes. These oscillators are coupled through a connecting tube whose length and diameter are varied as coupling parameters.

Malignant epidermoid arising from the third ventricle: A case report.

Background: Third epidermoid tumors are a rare finding. The appearance of these tumors often makes them difficult to diagnose, and thus they require multimodality imaging.

Case Summary: A 48-year-old male patient reported to our hospital with complaints of vomiting and severe headache.

Airway management techniques in head and neck cancer surgeries: a retrospective analysis.

Background: The aim of this study was to conduct a retrospective analysis of modalities of airway management and its impact on patients undergoing head and neck cancer surgeries.

Materials And Methods: A retrospective review of the medical record of 500 patients operated from January 2008 to December 2013 was conducted at our institute. Patients were reviewed for a mode of airway management, a total length of post-operative hospital stay (PLOS), and incidence of elderly patients in the total number of head and neck cancer surgeries posted for various diagnostic and definitive treatments.

Oral malignancy and its fickle blow off: A retrospective study.

Background: The aim of this study was to retrospectively evaluate various patterns of failure in patients with oral squamous cell carcinoma and to estimate overall survival (OS) and disease-free survival (DFS) in failure patterns.

Materials And Methods: Retrospective data of 500 patients operated for oral malignancy were obtained from year 2011 to 2014. Incidence of local, regional, and distant failure as well as DFS and OS was calculated.

Coupled interaction between unsteady flame dynamics and acoustic field in a turbulent combustor.

Thermoacoustic instability is a result of the positive feedback between the acoustic pressure and the unsteady heat release rate fluctuations in a combustor. We apply the framework of the synchronization theory to study the coupled behavior of these oscillations during the transition to thermoacoustic instability in a turbulent bluff-body stabilized gas-fired combustor. Furthermore, we characterize this complex behavior using recurrence plots and recurrence networks.

Effect of noise amplification during the transition to amplitude death in coupled thermoacoustic oscillators.

We present a systematic investigation of the effect of external noise on the dynamics of a system of two coupled prototypical thermoacoustic oscillators, horizontal Rijke tubes, using a mathematical model. We focus on the possibility of amplitude death (AD), which is observed in the deterministic model of coupled thermoacoustic oscillators as studied by Thomas [Chaos , 033119 (2018)], in the presence of noise. Although a complete cessation of oscillations or AD is not possible in the stochastic case, we observe a significant reduction in the amplitude of coupled limit cycle oscillations (LCOs) with the application of strong coupling.

Experimental Evidence of Amplitude Death and Phase-Flip Bifurcation between In-Phase and Anti-Phase Synchronization.

Nonlinear phenomena emerging from the coupled behaviour of a pair of oscillators have attracted considerable research attention over the years, of which, amplitude death (AD) and phase-flip bifurcation (PFB) are two noteworthy examples. Although theoretical research has postulated the coexistence of AD and PFB upon variation of different control parameters, such an occurrence has not been reported in practical systems. Here, we provide the first experimental evidence of the coexistence of AD and PFB in a physical system, comprising of a coupled pair of candle-flame oscillators.

Effect of time-delay and dissipative coupling on amplitude death in coupled thermoacoustic oscillators.

We here systematically investigate amplitude death (AD) phenomenon in a thermoacoustic system using a mathematical model of coupled prototypical thermoacoustic oscillators, the horizontal Rijke tubes. AD has recently been identified as a relatively simple phenomenon, which can be exploited to stop the unwanted high amplitude pressure oscillations resulting from the occurrence of thermoacoustic instability. We examine the effect of time-delay and dissipative couplings on a system of two Rijke tubes when they are symmetrically and asymmetrically coupled.

Characterization of forced response of density stratified reacting wake.

The hydrodynamic stability of a reacting wake depends primarily on the density ratio [i.e., ratio of unburnt gas density (ρ) to burnt gas density (ρ)] of the flow across the wake.

Fluorescence-based sensor for selective and sensitive detection of amoxicillin (Amox) in aqueous medium: Application to pharmaceutical and biomedical analysis.

We here for the first time demonstrate an analytical approach for the highly selective and sensitive detection of amoxicillin (Amox) in aqueous medium based on the fluorescence quenching of quantum dots (QDs). The change in fluorescence intensity of mercaptopropionic acid-capped cadmium sulphide (MPA-CdS) QDs is attributed to the increasing concentration of Amox. The results show that the fluorescence quenching of QDs by Amox takes place through both static and dynamic types of quenching mechanism.

CdS nanocrystals as fluorescent probe for detection of dolasetron mesylate in aqueous solution: Application to biomedical analysis.

A simple and straightforward method for the determination of dolasetron mesylate (DM) in aqueous solution was developed based on the fluorescence quenching of 3-Mercaptopropionic acid (MPA) capped CdS quantum dots (QDs). The structure, morphology, and optical properties of synthesized QDs were characterized by using UV-Vis absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements. Under the optimum conditions, the MPA-CdS QDs fluorescence probe offered good sensitivity and selectivity for detecting DM.

Spectroscopic Investigation of Interaction Between Carbon Quantum Dots and D-Penicillamine Capped Gold Nanoparticles.

This study reports the interaction and energy transfer between fluorescent carbon quantum dots (CQDs) and D-Penicillamine capped gold nanoparticles (DPA-AuNPs). The CQDs was synthesized by a simple chemical oxidation method at room temperature. The prepared CQDs shows a strong fluorescence at λ em  = 430 nm when excited at λ ex  = 320 nm.