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1.
J Biomol Struct Dyn ; : 1-21, 2020 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-32396767

RESUMO

The recent outbreak of novel "coronavirus disease 2019" (COVID-19) has spread rapidly worldwide, causing a global pandemic. In the present work, we have elucidated the mechanism of binding of two inhibitors, namely α-ketoamide and Z31792168, to SARS-CoV-2 main protease (Mpro or 3CLpro) by using all-atom molecular dynamics simulations and free energy calculations. We calculated the total binding free energy (ΔGbind) of both inhibitors and further decomposed ΔGbind into various forces governing the complex formation using the Molecular Mechanics/Poisson-Boltzmann Surface Area (MM/PBSA) method. Our calculations reveal that α-ketoamide is more potent (ΔGbind= - 9.05 kcal/mol) compared to Z31792168 (ΔGbind= - 3.25 kcal/mol) against COVID-19 3CLpro. The increase in ΔGbind for α-ketoamide relative to Z31792168 arises due to an increase in the favorable electrostatic and van der Waals interactions between the inhibitor and 3CLpro. Further, we have identified important residues controlling the 3CLpro-ligand binding from per-residue based decomposition of the binding free energy. Finally, we have compared ΔGbind of these two inhibitors with the anti-HIV retroviral drugs, such as lopinavir and darunavir. It is observed that α-ketoamide is more potent compared to lopinavir and darunavir. In the case of lopinavir, a decrease in van der Waals interactions is responsible for the lower binding affinity compared to α-ketoamide. On the other hand, in the case of darunavir, a decrease in the favorable intermolecular electrostatic and van der Waals interactions contributes to lower affinity compared to α-ketoamide. Our study might help in designing rational anti-coronaviral drugs targeting the SARS-CoV-2 main protease.

2.
J Biomol Struct Dyn ; : 1-16, 2020 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-32000612

RESUMO

Acquired immune deficiency syndrome (AIDS) is caused by the human immunodeficiency virus (HIV), type 1 and 2. Further, the diversity in HIV-1 has given rise to many serotypes and recombinant strains. The currently used protease inhibitors have been developed for subtype B, although non-B subtype strains account for ∼ 90% of the global HIV infections. Subtype D is spreading rapidly and infecting a large population in North Africa and the Middle East. In the current study, molecular dynamics simulations in conjunction with the molecular mechanics/Poisson-Boltzmann surface area (MM-PBSA) scheme was used to investigate the potency of four drugs, namely atazanavir (ATV), darunavir (DRV), lopinavir (LPV) and tipranavir (TPV) against the subtype D variant. Our calculations predicted that the potency of the inhibitors decreased in the order TPV > ATV > DRV > LPV. TPV was found to be the most potent against subtype D due to an increase in van der Waals and electrostatic interactions and reduction in the desolvation energy compared to other inhibitors. This result is further supported by the hydrogen bond interactions between inhibitors and protease. Furthermore, our analyses suggested that the binding of TPV induced a more closed conformation of the flap compared to apo or other complexes. It was observed that TPV/PRD has a lower cavity volume relative to the other three complexes leading to a tighter binding. The open conformation of the flap was observed for LPV/PRD. We expect that this study might be useful for designing more potent inhibitors against HIV-1 subtype D.Communicated by Ramaswamy H. Sarma.

3.
Nanoscale ; 12(7): 4452-4458, 2020 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-32030395

RESUMO

Metallicity of nanoparticles can be defined in different ways. One possibility is to look at the degree to which external fields are screened inside the object. This screening would be complete in a classical perfect metal where surface charges arrange on the classical -i.e., abrupt - surface such that no internal fields exist. However, it is obvious that this situation is modified for very small clusters: the surface charges are "smeared out" at the surface, and the screening might be less complete. In the present work we ask the question as to how close small noble-metal clusters are to a classical metal. We show that, indeed, the screening is almost complete (≈96%) already for as little as one atomic layer of the coinage metals, silver and gold alike. At the same time, we show that quantum effects, viz., electronic shell closings and the Friedel-like oscillations of the density, play a role, meaning that the clusters cannot be described solely using the concept of screening in a classical metal.

4.
Int J Mol Sci ; 21(3)2020 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-31991583

RESUMO

Mammalian heart valves are soft tissue assemblies with multi-scale material properties. This is because they are constructs comprising both muscle and non-contractile extracellular matrix proteins (such as collagens and proteoglycans) and transition regions where one form of tissue structure becomes another, significantly different form. The leaflets of the mitral and tricuspid valves are connected to chordae tendinae which, in turn, bind through papillary muscles to the cardiac wall of the ventricle. The transition regions between these tissue subsets are complex and diffuse. Their material composition and mechanical properties have not been previously described with both micro and nanoscopic data recorded simultaneously, as reported here. Annotating the mechanical characteristics of these tissue transitions will be of great value in developing novel implants, improving the state of the surgical simulators and advancing robot-assisted surgery. We present here developments in multi-scale methodology that produce data that can relate mechanical properties to molecular structure using scanning X-ray diffraction. We correlate these data to corresponding tissue level (macro and microscopic) stress and strain, with particular emphasis on the transition regions and present analyses to indicate points of possible failure in these tissues.

5.
Phys Rev Lett ; 123(15): 154101, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31702295

RESUMO

A new type of dynamics called laminar chaos was recently discovered through a theoretical analysis of a scalar delay differential equation with time-varying delay. Laminar chaos is a low-dimensional dynamics characterized by laminar phases of nearly constant intensity with periodic durations and a chaotic variation of the intensity from one laminar phase to the next laminar phase. This is in stark contrast to the typically observed higher-dimensional turbulent chaos, which is characterized by strong fluctuations. In this Letter we provide the first experimental observation of laminar chaos by studying an optoelectronic feedback loop with time-varying delay. The noise inherent in the experiment requires the development of a nonlinear Langevin equation with variable delay. The results show that laminar chaos can be observed in higher-order systems, and that the phenomenon is robust to noise and a digital implementation of the variable time delay.

6.
Philos Trans A Math Phys Eng Sci ; 377(2153): 20180123, 2019 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-31329059

RESUMO

We present a systematic approach to reveal the correspondence between time delay dynamics and networks of coupled oscillators. After early demonstrations of the usefulness of spatio-temporal representations of time-delay system dynamics, extensive research on optoelectronic feedback loops has revealed their immense potential for realizing complex system dynamics such as chimeras in rings of coupled oscillators and applications to reservoir computing. Delayed dynamical systems have been enriched in recent years through the application of digital signal processing techniques. Very recently, we have showed that one can significantly extend the capabilities and implement networks with arbitrary topologies through the use of field programmable gate arrays. This architecture allows the design of appropriate filters and multiple time delays, and greatly extends the possibilities for exploring synchronization patterns in arbitrary network topologies. This has enabled us to explore complex dynamics on networks with nodes that can be perfectly identical, introduce parameter heterogeneities and multiple time delays, as well as change network topologies to control the formation and evolution of patterns of synchrony. This article is part of the theme issue 'Nonlinear dynamics of delay systems'.

7.
Phys Rev Lett ; 122(5): 058301, 2019 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-30822003

RESUMO

Symmetries are ubiquitous in network systems and have profound impacts on the observable dynamics. At the most fundamental level, many synchronization patterns are induced by underlying network symmetry, and a high degree of symmetry is believed to enhance the stability of identical synchronization. Yet, here we show that the synchronizability of almost any symmetry cluster in a network of identical nodes can be enhanced precisely by breaking its structural symmetry. This counterintuitive effect holds for generic node dynamics and arbitrary network structure and is, moreover, robust against noise and imperfections typical of real systems, which we demonstrate by implementing a state-of-the-art optoelectronic experiment. These results lead to new possibilities for the topological control of synchronization patterns, which we substantiate by presenting an algorithm that optimizes the structure of individual clusters under various constraints.

9.
Chaos ; 29(12): 121104, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31893648

RESUMO

We introduce and test a general machine-learning-based technique for the inference of short term causal dependence between state variables of an unknown dynamical system from time-series measurements of its state variables. Our technique leverages the results of a machine learning process for short time prediction to achieve our goal. The basic idea is to use the machine learning to estimate the elements of the Jacobian matrix of the dynamical flow along an orbit. The type of machine learning that we employ is reservoir computing. We present numerical tests on link inference of a network of interacting dynamical nodes. It is seen that dynamical noise can greatly enhance the effectiveness of our technique, while observational noise degrades the effectiveness. We believe that the competition between these two opposing types of noise will be the key factor determining the success of causal inference in many of the most important application situations.

10.
J Chem Theory Comput ; 14(12): 6417-6426, 2018 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-30404453

RESUMO

Time-dependent density-functional theory (TDDFT) is widely used for calculating electron excitations in clusters and large molecules. For optical excitations, TDDFT is customarily applied in two distinct approaches: transition-based linear-response TDDFT (LR-TDDFT) and the real-time formalism (RT-TDDFT). The former directly provides the energies and transition densities of the excitations, but it requires the calculation of a large number of empty electron states, which makes it cumbersome for large systems. By contrast, RT-TDDFT circumvents the evaluation of empty orbitals, which is especially advantageous when dealing with large systems. A drawback of the procedure is that information about the nature of individual spectral features is not automatically obtained, although it is of course contained in the time-dependent induced density. Fourier transform of the induced density has been used in some simple cases, but the method is, surprisingly, not widely used to complement the RT-TDDFT calculations; although the reliability of RT-TDDFT spectra is now widely accepted, a critical assessment for the corresponding transition densities and a demonstration of the technical feasibility of the Fourier-transform evaluation for general cases is still lacking. In the present work, we show that the transition densities of the optically allowed excitations can be efficiently extracted from a single δ-kick time-evolution calculation even in complex systems like noble metals. We assess the results by comparison with the corresponding LR-TDDFT ones and also with the induced densities arising from RT-TDDFT simulations of the excitation process.

11.
Nanoscale ; 10(35): 16822-16829, 2018 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-30167606

RESUMO

Graphene-based van der Waals (vdW) heterostructures can facilitate exciting charge transfer dynamics in between structural layers with the emission of excitonic quasi-particles. However, the chemical formation of such heterostructures has been elusive thus far. In this work, a simple chemical approach is described to form such van der Waals (vdW) heterostructures using few layer MoS2 sheet embedded quantum dots (QDs) and amine-functionalized graphene quantum dots (GQDs) to probe the energy transfer mechanism for tunable photoluminescence (PL). Our findings reveal an interesting non-radiative Förster-type energy transfer with the quenching of functional GQD PL intensity after GQD/MoS2 composite formation, which validates the existing charge transfer dynamics analogous to 0D and 2D systems. The non-radiative type of energy transfer characteristic from GQD into the MoS2 layer through vdW interactions has been confirmed by photoluminescence, time decay analyses and ab initio calculations with the shifting of the Fermi level in the density of states towards the conduction band in the stacked configuration. These results are encouraging for the fundamental exploration of optical properties in other chemically prepared QD/2D based heterostructures to understand the charge transfer mechanism and fingerprint luminescence quenching for future optoelectronic device and optical sensing applications.

12.
Nucl Med Commun ; 39(7): 628-635, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29672466

RESUMO

OBJECTIVES: This study aims to assess the correlation between PET/CT and endoscopic ultrasound (EUS) parameters in patients with oesophageal cancer. PATIENTS AND METHODS: All patients who had complete PET/CT and EUS staging performed for oesophageal cancer at our centre between 2010 and 2016 were included. Images were retrieved and analysed for a range of parameters including tumour length, volume and position relative to the aortic arch. RESULTS: Seventy patients were included in the main analysis. A strong correlation was found between EUS and PET/CT in the tumour length, the volume and the position of the tumour relative to the aortic arch. Regression modelling showed a reasonable predictive value for PET/CT in calculating EUS parameters, with r higher than 0.585 in some cases. CONCLUSION: Given the strong correlation between EUS and PET parameters, fluorine-18 fluorodeoxyglucose (F-FDG) PET can provide accurate information on the length and the volume of tumour in patients who either cannot tolerate EUS or have impassable strictures.


Assuntos
Endossonografia , Neoplasias Esofágicas/diagnóstico por imagem , Fluordesoxiglucose F18 , Tomografia Computadorizada com Tomografia por Emissão de Pósitrons , Idoso , Neoplasias Esofágicas/patologia , Neoplasias Esofágicas/cirurgia , Feminino , Humanos , Masculino , Carga Tumoral
13.
Lancet Gastroenterol Hepatol ; 3(2): 114-124, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29248399

RESUMO

BACKGROUND: A short course of radiotherapy is commonly prescribed for palliative relief of malignant dysphagia in patients with incurable oesophageal cancer. We compared chemoradiotherapy with radiotherapy alone for dysphagia relief in the palliative setting. METHODS: This multicentre randomised controlled trial included patients with advanced or metastatic oesophageal cancer who were randomly assigned (1:1) through a computer-generated adaptive biased coin design to either palliative chemoradiotherapy or radiotherapy alone for treatment of malignant dysphagia at 22 hospitals in Australia, Canada, New Zealand, and the UK. Eligible patients had biopsy-proven oesophageal cancer that was unsuitable for curative treatment, symptomatic dysphagia, Eastern Cooperative Oncology Group performance status 0-2, and adequate haematological and renal function. Patients were stratified by hospital, dysphagia score (Mellow scale 1-4), and presence of metastases. The radiotherapy dose was 35 Gy in 15 fractions over 3 weeks for patients in Australia and New Zealand and 30 Gy in ten fractions over 2 weeks for patients in Canada and the UK. Chemotherapy consisted of one cycle of intravenous cisplatin (either 80 mg/m2 on day 1 or 20 mg/m2 per day on days 1-4 of radiotherapy at clinician's discretion) and intravenous fluorouracil 800 mg/m2 per day on days 1-4 of radiotherapy in week 1. Patients were assessed weekly during treatment. The primary endpoint was dysphagia relief (defined as ≥1 point reduction on the Mellow scale at 9 weeks and maintained 4 weeks later), and key secondary endpoints were dysphagia progression-free survival (defined as a worsening of at least 1 point on the Mellow scale from baseline or best response) and overall survival. These endpoints were analysed in the intention-to-treat population. This study is registered at ClinicalTrials.gov, number NCT00193882. This trial is closed. FINDINGS: Between July 7, 2003, and March 21, 2012, 111 patients were randomly assigned to chemoradiotherapy and 109 patients to radiotherapy. One patient in the chemoradiotherapy group was omitted from analysis because of ineligibility. 50 (45%, 95% CI 36-55) patients in the chemoradiotherapy group and 38 (35%, 26-44) in the radiotherapy group obtained dysphagia relief (difference 10·6%, 95% CI -2 to 23; p=0·13). Median dysphagia progression-free survival was 4·1 months (95% CI 3·5-4·8) versus 3·4 months (3·1-4·3) in the chemoradiotherapy and radiotherapy groups, respectively (p=0·58), and median overall survival was 6·9 months (95% CI 5·1-8·3) versus 6·7 months (4·9-8·0), respectively (p=0·88). Of the 211 patients who commenced radiotherapy, grade 3-4 acute toxicity occurred in 38 (36%) patients in the chemoradiotherapy group and in 17 (16%) patients in the radiotherapy group (p=0·0017). Anaemia, thrombocytopenia, neutropenia, oesophagitis, diarrhoea, nausea and vomiting, and mucositis were significantly worse in patients who had chemoradiotherapy than in patients who had radiotherapy. INTERPRETATION: Palliative chemoradiotherapy showed a modest, but not statistically significant, increase in dysphagia relief compared with radiotherapy alone, with minimal improvement in dysphagia progression-free survival and overall survival with chemoradiotherapy but at a cost of increased toxicity. A short course of radiotherapy alone should be considered a safe and well tolerated treatment for malignant dysphagia in the palliative setting. FUNDING: National Health and Medical Research Council, Canadian Cancer Society Research Institute, Canadian Cancer Trials Group, Trans Tasman Radiation Oncology Group, and Cancer Australia.


Assuntos
Transtornos de Deglutição/terapia , Neoplasias Esofágicas/complicações , Cuidados Paliativos/métodos , Idoso , Idoso de 80 Anos ou mais , Antineoplásicos/uso terapêutico , Quimiorradioterapia/efeitos adversos , Cisplatino/uso terapêutico , Transtornos de Deglutição/etiologia , Neoplasias Esofágicas/patologia , Feminino , Fluoruracila/uso terapêutico , Humanos , Análise de Intenção de Tratamento , Masculino , Pessoa de Meia-Idade , Metástase Neoplásica , Radioterapia/efeitos adversos , Análise de Sobrevida
14.
J Phys Condens Matter ; 29(37): 375701, 2017 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-28664872

RESUMO

For weak or moderate doping, electrical measurement is not suitable for detecting changes in the charge localization inside a semiconductor. Here, to investigate the nature of charge-phonon coupling in the presence of gradually delocalized holes within a weak doping regime (~1016 cm-3), we examine the temperature dependent Raman spectra (303-817 K) of prototype hole doped delafossite [Formula: see text] (x = 0/0.03, y = 0/0.01). For both [Formula: see text] and [Formula: see text] phonons, negative lineshape asymmetry and relative thermal hardening are distinctly observed upon [Formula: see text] and [Formula: see text] doping. Using Allen formalism, charge density of states at the Fermi level per spin and molecule, and charge delocalization associated to [Formula: see text] plane, are estimated to increase appreciably upon codoping compared to the [Formula: see text]-axis. We delineate the interdependence between charge-phonon coupling constant ([Formula: see text]) and anharmonic phonon lifetime ([Formula: see text]), and deduce that excitation of delocalized holes weakly coupled with phonons of larger [Formula: see text] is the governing feature of observed Fano asymmetry ([Formula: see text]) reversal.

15.
Eur J Cancer ; 74: 38-46, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-28335886

RESUMO

BACKGROUND: Oxaliplatin-capecitabine (OxCap) and carboplatin-paclitaxel (CarPac) based neo-adjuvant chemoradiotherapy (nCRT) have shown promising activity in localised, resectable oesophageal cancer. PATIENTS AND METHODS: A non-blinded, randomised (1:1 via a centralised computer system), 'pick a winner' phase II trial. Patients with resectable oesophageal adenocarcinoma ≥ cT3 and/or ≥ cN1 were randomised to OxCapRT (oxaliplatin 85 mg/m2 day 1, 15, 29; capecitabine 625 mg/m2 bd on days of radiotherapy) or CarPacRT (carboplatin AUC2; paclitaxel 50 mg/m2 day 1, 8, 15, 22, 29). Radiotherapy dose was 45 Gy/25 fractions/5 weeks. Both arms received induction OxCap chemotherapy (2 × 3 week cycles of oxaliplatin 130 mg/m2 day 1, capecitabine 625 mg/m2 bd days 1-21). Surgery was performed 6-8 weeks after nCRT. Primary end-point was pathological complete response (pCR). Secondary end-points included toxicity, surgical morbidity/mortality, resection rate and overall survival. STATISTICS: Based on pCR ≤ 15% not warranting future investigation, but pCR ≥ 35% would, 76 patients (38/arm) gave 90% power (one-sided alpha 10%), implying that arm(s) having ≥10 pCR out of first 38 patients could be considered for phase III trials. ClinicalTrials.gov: NCT01843829. Funder: Cancer Research UK (C44694/A14614). RESULTS: Eighty five patients were randomised between October 2013 and February 2015 from 17 UK centres. Three of 85 (3.5%) died during induction chemotherapy. Seventy-seven patients (OxCapRT = 36; CarPacRT = 41) underwent surgery. The 30-d post-operative mortality was 2/77 (2.6%). Grade III/IV toxicity was comparable between arms, although neutropenia was higher in the CarPacRT arm (21.4% versus 2.6%, p = 0.01). Twelve of 41 (29.3%) (10 of first 38 patients) and 4/36 (11.1%) achieved pCR in the CarPacRT and OxcapRT arms, respectively. Corresponding R0 resection rates were 33/41 (80.5%) and 26/36 (72.2%), respectively. CONCLUSION: Both regimens were well tolerated. Only CarPacRT passed the predefined pCR criteria for further investigation.


Assuntos
Adenocarcinoma/terapia , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Neoplasias Esofágicas/terapia , Administração Oral , Idoso , Capecitabina/administração & dosagem , Capecitabina/efeitos adversos , Carboplatina/administração & dosagem , Carboplatina/efeitos adversos , Quimiorradioterapia Adjuvante/métodos , Feminino , Humanos , Infusões Intravenosas , Masculino , Pessoa de Meia-Idade , Terapia Neoadjuvante/métodos , Compostos Organoplatínicos/administração & dosagem , Compostos Organoplatínicos/efeitos adversos , Oxaliplatina , Paclitaxel/administração & dosagem , Paclitaxel/efeitos adversos , Cuidados Pré-Operatórios/métodos , Resultado do Tratamento
16.
Chaos ; 27(12): 121103, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-29289048

RESUMO

We report a new experimental approach using an optoelectronic feedback loop to investigate the dynamics of oscillators coupled on large complex networks with arbitrary topology. Our implementation is based on a single optoelectronic feedback loop with time delays. We use the space-time interpretation of systems with time delay to create large networks of coupled maps. Others have performed similar experiments using high-pass filters to implement the coupling; this restricts the network topology to the coupling of only a few nearest neighbors. In our experiment, the time delays and coupling are implemented on a field-programmable gate array, allowing the creation of networks with arbitrary coupling topology. This system has many advantages: the network nodes are truly identical, the network is easily reconfigurable, and the network dynamics occur at high speeds. We use this system to study cluster synchronization and chimera states in both small and large networks of different topologies.

17.
Stapp Car Crash J ; 61: 175-209, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29394439

RESUMO

Improving injury prediction accuracy and fidelity for mounted Warfighters has become an area of focus for the U.S. military in response to improvised explosive device (IED) use in both Iraq and Afghanistan. Although the Hybrid III anthropomorphic test device (ATD) has historically been used for crew injury analysis, it is only capable of predicting a few select skeletal injuries. The Computational Anthropomorphic Virtual Experiment Man (CAVEMAN) human body model is being developed to expand the injury analysis capability to both skeletal and soft tissues. The CAVEMAN model is built upon the Zygote 50th percentile male human CAD model and uses a finite element modeling approach developed for high performance computing (HPC). The lower extremity subset of the CAVEMAN human body model presented herein includes: 28 bones, 26 muscles, 40 ligaments, fascia, cartilage and skin. Sensitivity studies have been conducted with the CAVEMAN lower extremity model to determine the structures critical for load transmission through the leg in the underbody blast (UBB) environment. An evaluation of the CAVEMAN lower extremity biofidelity was also carried out using 14 unique data sets derived by the Warrior Injury Assessment Manikin (WIAMan) program cadaveric lower leg testing. Extension of the CAVEMAN lower extremity model into anatomical tissue failure will provide additional injury prediction capabilities, beyond what is currently achievable using ATDs, to improve occupant survivability analyses within military vehicles.


Assuntos
Traumatismos por Explosões , Simulação por Computador , Explosões , Traumatismos da Perna , Lesões Relacionadas à Guerra , Aceleração , Fenômenos Biomecânicos , Cadáver , Análise de Elementos Finitos , Humanos , Extremidade Inferior , Masculino , Manequins , Militares , Modelos Biológicos , Suporte de Carga
18.
Chaos ; 26(9): 094801, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27781456

RESUMO

A "chimera state" is a dynamical pattern that occurs in a network of coupled identical oscillators when the symmetry of the oscillator population is broken into synchronous and asynchronous parts. We report the experimental observation of chimera and cluster states in a network of four globally coupled chaotic opto-electronic oscillators. This is the minimal network that can support chimera states, and our study provides new insight into the fundamental mechanisms underlying their formation. We use a unified approach to determine the stability of all the observed partially synchronous patterns, highlighting the close relationship between chimera and cluster states as belonging to the broader phenomenon of partial synchronization. Our approach is general in terms of network size and connectivity. We also find that chimera states often appear in regions of multistability between global, cluster, and desynchronized states.

19.
ACS Appl Mater Interfaces ; 8(38): 25571-7, 2016 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-27166784

RESUMO

Field-emission displays (FEDs) constitute one of the major foci of the cutting edge materials research because of the increasingly escalating demand for high-resolution display panels. However, poor efficiencies of the concurrent low voltage cathodoluminescence (CL) phosphors have created a serious bottleneck in the commercialization of such devices. Herein we report a novel CuI-RGO composite nanophosphor that exhibits bright red emission under low voltage electron beam excitation. Quantitative assessment of CL spectra reveals that CuI-RGO nanocomposite phosphor leads to the 4-fold enhancement in the CL intensity as compared to the pristine CuI counterpart. Addition of RGO in the CuI matrix facilitates efficient triggering of luminescence centers that are activated by local electric field enhancement at the CuI-RGO contact points. In addition, conducting RGO also reduces the negative loading problem on the surface of the nanophosphor composite. The concept presented here opens up a novel generic route for enhancing CL intensity of the existing (nano)phosphors as well as validates the bright prospects of the CuI-RGO composite nanophosphor in this rapidly growing field.

20.
Sci Adv ; 2(4): e1501737, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-27152349

RESUMO

Synchronization is an important and prevalent phenomenon in natural and engineered systems. In many dynamical networks, the coupling is balanced or adjusted to admit global synchronization, a condition called Laplacian coupling. Many networks exhibit incomplete synchronization, where two or more clusters of synchronization persist, and computational group theory has recently proved to be valuable in discovering these cluster states based on the topology of the network. In the important case of Laplacian coupling, additional synchronization patterns can exist that would not be predicted from the group theory analysis alone. Understanding how and when clusters form, merge, and persist is essential for understanding collective dynamics, synchronization, and failure mechanisms of complex networks such as electric power grids, distributed control networks, and autonomous swarming vehicles. We describe a method to find and analyze all of the possible cluster synchronization patterns in a Laplacian-coupled network, by applying methods of computational group theory to dynamically equivalent networks. We present a general technique to evaluate the stability of each of the dynamically valid cluster synchronization patterns. Our results are validated in an optoelectronic experiment on a five-node network that confirms the synchronization patterns predicted by the theory.


Assuntos
Sistemas Computacionais , Física , Eletricidade , Modelos Teóricos , Dinâmica não Linear
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