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Ionospheric plasma introduces nonlinear perturbations in regular EM wave propagation which in turn affects the signal transmission in a highly nonlinear manner. Often the signals are distorted by a varied degree of nonlinearity. The wireless communication mechanism is affected by small perturbations which take gigantic rogue wave structures with the possibility of damaging sophisticated equipments. To study the evolution of rogue wave-type solitons starting from initial small-amplitude perturbations, we have considered a three-component electron–ion plasma system with degeneracy pressure as well as quantum diffraction effects. A solitary wave structure is formed due to the interplay of nonlinear and dispersive forces. Such a formation under an external force gets modified and the stability criteria are altered. The interesting fact thus obtained here shows that relativistic and thermal degeneracy favour stability whereas quantum diffraction leads to instability. In this paper, we have studied how solitary wave structures behave under an external force. Next, we study how the nonlinear effects cause an amplitude modulation and the envelope soliton is formed. Such an envelope soliton is studied by the nonlinear Schrödinger equation that we derive in the later part of the work. We have carried out simulation studies and compared our results with the analytical findings of other workers. [ABSTRACT FROM AUTHOR]

We present an algorithm to predict the linear relaxation spectra for linear polymers of fully general and arbitrary polydispersity. As is common in the tube theory descriptions of linear polymers, we assume that the stress relaxation is affected by both the constraint release and tube escape modes, but unlike most existing descriptions we consider how these two modes of relaxation affect each other. We argue that the proper description for relaxation in an arbitrary blend of linear polymers requires consideration of multiple embedded tubes affecting the different relaxation pathways; we propose a novel but minimal description involving five embedded tubes. Building on prior work for binary blends, we derive the scaling level descriptions of the relaxation pathways. We use a large number of existing experimental results on the stress and dielectric relaxations to validate our model, ensuring we explore a very broad range of parameter space. [ABSTRACT FROM AUTHOR]

We considered a dense plasma containing electrons, positrons, ions and dust particles in background magnetic and gravitational fields alongside collisional effects for the heavier species (ions and dust particles). Such plasmas are found in magnetars, black hole accretion disks, and so on. The quantum hydrodynamic (QHD) model was used to construct the governing equations of the plasma. Relativistic degeneracy pressure is taken as the equation of state for the electrons and positrons. Effects of exchange-correlation potential were also considered for the lighter species. We employed the reductive perturbation method (RPM) in order to obtain the Zakharov–Kuznetsov (ZK) equation describing 3-D ion acoustic waves (IAWs) with minimal lateral perturbations. Low order analytical solutions allow us to understand the parametric dependence of said structures. Our newly developed numerical technique: homotopy assisted symbolic simulation (HASS) sheds light on the gradual evolution of higher order stationary formations in the system. The results thus obtained can potentially explain certain astrophysical phenomena as well as dense laboratory plasmas. [ABSTRACT FROM AUTHOR]

In this work, we used the semi-Lagrangian method and the Vlasov code to study the instabilities in a quantum plasma with 1-D temperature anisotropy. Taking the Fermi–Dirac type of distribution function (DF) and using the semi-Lagrangian Vlasov code, we studied the gradual evolution of density and kinetic energy in a degenerate plasma with quantum effects. In this collisionless plasma, adiabatic compression will be along the direction of wave propagation and will lead to temperature anisotropy of the electron distribution that varies along the direction of wave propagation. The findings will find application for dense plasma at finite temperature as in laser-produced plasmas, fusion plasma, as well as solar plasmas. [ABSTRACT FROM AUTHOR]

In this article, we investigate the linear and nonlinear behavior of ion-plasma waves in a two-component plasma containing ions and dust particles. We have studied the linear dispersion characteristics, nonlinear KdV solitons, and amplitude modulated electrostatic waves. Such ion-plasma wave modes in dust-ion plasma have been theoretically investigated by incorporating quantum diffraction and relativistic effects. Numerical analysis of the linear dispersion relation with variations of different parameters has been carried out. By employing the reductive perturbation technique the KdV equation describing the small amplitude solitary profile has been studied. Using the standard multiple scale perturbation method, a nonlinear Schrödinger (NLS) equation has been derived by including quantum and relativistic effects, which describes the nonlinear evolution of the ion-plasma waves in dust-ion plasma. The wave is found to become modulationally unstable beyond certain critical wavenumber. The critical wavenumber and the growth rate of modulational instability are shown to depend significantly on the relativistic motion of plasma particles and the quantum diffraction effect. The results presented in the article are expected to be helpful for understanding the propagation of finite amplitude ion-plasma waves in some laboratory and astrophysical plasma systems. PACS—52.59.Hq, 67.10.Jn, 52.20 −j, 52.25 −b, 52.30 −d, 52.35 Mw, 52.65 Vv [ABSTRACT FROM AUTHOR]

Impedance-source-based solar PV systems are capable of achieving both voltage boosting and inversion in a single stage, resulting in a simple design thereby enhancing reliability. One of the major concerns of PV systems is their leakage current, as it can cause hazardous operational insecurity and reliability. This article introduces a quasi-Z-source (qZS)-based five-level inverter, which displays the following advantages: 1) reactive power handling capability, 2) single-stage boosting, 3) shoot-through immunity, and 4) reduced leakage current based on VDE 0126-1-1. The proposed single-stage power converter is constituted by the fusion of a boosting stage, consisting of two back-to-back connected qZSs, with a five-level inverter produced by the combination of T-type and neutral point clamped arms. The problem of the leakage current is addressed by a modified modulation technique and a passive filter structure, which filters high-frequency variations in the common mode voltage. The working principle of the proposed power converter and the effectiveness of the modulation scheme to reduce the leakage current are assessed with the aid of simulation studies in both standalone and the grid-connected modes. The simulation results are experimentally validated with the aid of a laboratory prototype of 500 W rating. [ABSTRACT FROM AUTHOR]

Grid‐connected Single‐Stage Boost Inverters (SSBI) are extensively being researched in the area of photovoltaic energy conversion systems. Owing to their single‐stage boosting capability, this class of power converters results in higher efficiency and reliability. This power circuit configuration is constituted by two mutually dependent sub‐converters, in that a front‐end quasi‐Z‐source (qZS) part is integrated to a back‐end multilevel inverter (MLI). The MLI provides the shoot‐through state to the qZS, while the qZS provides the pulsating DC input to the MLI. In general, solar photovoltaic inverters suffer from the disadvantage of leakage current that flows from solar panels to the grid/load. This paper introduces a dual quasi‐Z‐source based multilevel inverter, which achieves the following benefits: (a) five‐level output voltage, (b) reactive power capability, (c) shoot‐through immunity, (d) continuous input current, and (e) reduced leakage current based on VDE 0126‐1‐1 standards. In this paper, a modified modulation scheme, which is based on the employment of phase‐disposed and level‐shifted carrier signals, has been used to reduce the leakage current. To reduce the leakage current further, a passive filter is employed to eliminate high frequency variations across the parasitic capacitance. The working principle of the proposed power converter and the effectiveness of the modulation scheme have been validated with simulation studies in both standalone and the grid‐connected mode. Finally, the simulation studies are verified through an experimental prototype of 500 W rating. [ABSTRACT FROM AUTHOR]

In this paper we have studied the gradual evolution of stationary formations in electron acoustic waves at a finite temperature quantum plasma. We have made use of Quantum hydrodynamics model equations and obtained the KdV-Burgers equation. From here we showed how the amplitude modulated solitons evolve from double layer structures through shock fronts and ultimately converging into solitary structures. We have studied the various parametric influences on such stationary structure and also showed how the gradual variations of these parameter affect the transition from one form to another. The results thus obtained will help in the generation and structure of the structures in their respective domain. Much of the experiments on dense plasma will benefit from the parametric study. Further we have studied amplitude modulation followed by a detailed study on chaos. [ABSTRACT FROM AUTHOR]

We studied the nonlinear evolution of an amplitude-modulated envelop soliton formed in a dense plasma when a laser beam interacts with it. The employment of our newly developed technique, homotopy-assisted symbolic simulation, has been instrumental in the study of the nature and formation of envelope solitons and their dependence on various parameters. The different orders of homotopy perturbation generate a convergent series solution for such nonlinear coupled partial differential equations (PDE). Our technique bypasses the rigorous analytical derivation of coupled PDE without a loss of information. The methodology is very novel and holds promise for application in models that explain experimental observations. The results will be beneficial in interpreting various dense laser plasma interactions. [ABSTRACT FROM AUTHOR]

Impedance source-based multilevel inverters are becoming popular for emerging power generation technologies such as fuel cells, photovoltaic, and wind turbines. It is one of the most promising power electronic interfaces for single stage DC/AC conversion with inherent buck-boost capability. Therefore, in this paper, an extensive review of emerging impedance source-based multilevel inverter (Z-MLI) topologies is presented. These topologies are developed by the combination of impedance source network and multilevel inverter (MLI) with the merits of high voltage gain, enhanced reliability due to shoot-through immunity, improved input voltage regulation, reduced filter size, and better quality of supply. Most of the recent Z-MLI topologies are based on quasi-Z-source network which operates with continuous input current. In order to identify a suitable topology, an exhaustive comparison is made with various configurations of Z-MLIs in terms of component count, boost gain, switching stress, and control complexity. [ABSTRACT FROM AUTHOR]

In this theoretical study, we investigate the amplitude modulation and envelop soliton formation in a dense plasma when such a plasma interacts with a strong laser beam. We have made use of the symbolic simulation technique to find the modulation instability of an electrostatic wave with higher orders of non‐linearity. We identified the range of wavenumber in which such non‐linearity is important. Furthermore, we have analysed the formation of envelope soliton of waves localized in space. The results obtained here will be helpful in interpreting different phenomena that arise in laser plasma interaction. The importance of the relativistic contribution of streaming particles is discussed alongside the parametric influences experienced by the plasma particles. [ABSTRACT FROM AUTHOR]

Using thermodynamic integration, we calculate free energies of the melt and the crystalline phases of a model system of C[SUB198]H[SUB398] with a realistic all-atom potential. We use the Gibbs-Duhem integration scheme to calculate the melting curve over the experimentally relevant pressure range. The crystal structure and the melting curve obtained from our simulation are in good quantitative agreement with the available experimental results. Using thermodynamic integration, we calculate free energies of the melt and the crystalline phases of a model system of C[SUB198]H[SUB398] with a realistic all-atom potential. We use the Gibbs-Duhem integration scheme to calculate the melting curve over the experimentally relevant pressure range. The crystal structure and the melting curve obtained from our simulation are in good quantitative agreement with the available experimental results. [ABSTRACT FROM AUTHOR]

Advance in computational rheology allows for in silico predictions of the viscoelastic responses of arbitrarily branched polymer melts. While detailed branching structure is required for the rheology predictions, rheology itself is often the most sensitive tool to detect low levels of branching. With rheological experiments and computational modeling of a set of nominally linear and model comb ethylene-butene copolymers, we show that coupled models for the synthesis and rheology can integrate diverse measurements, incorporating inherent experimental uncertainties. This approach allows us to achieve tight bounds on the branching structures of the constituent molecules. Next, we numerically explore the effects of the numbers and molar masses of side arms in comb polymers on the viscoelastic responses in both the linear and nonlinear regimes. Such computational exploration can aid in designing specific polymers suitable for a given processing scenario. Graphical abstract Coupled models for synthesis and rheology allow tight bounds on branching architecture and parametric exploration of flow properties of statistically branched polymers. [ABSTRACT FROM AUTHOR]

Because of the familiarity of gelation theories in polycondensation reaction of multifunctional groups, often the gel-point is defined as the point of diverging weight averaged molar mass. The authors present an industrially relevant counter-example to this common perception. Chain-growth polymerization in realistic reactors introduces history dependent crosslinking probability. For copolymerization of a two functional monomer (ethylene) with a four functional comonomer (nonconjugated diene), the authors show from a Monte Carlo scheme that standard gelation scaling exponents remain valid for a semibatch reactor. However, for syntheses in a continuous stirred tank reactor (CSTR), all commonly measured molar mass moments (number, weight and ' z'-averaged moment) remain finite at the gel-point; the first moment to diverge is the fourth moment. Hence, identification of the gel point from experimental observations is difficult, and cannot be achieved through monitoring of the weight averaged molar mass. The authors use a numerical scheme based on the tube model of polymer melts to predict the rheology of the generated molecules. Stress relaxation follows a power-law decay, but due to dynamic dilution effects the CSTR resins exhibit much slower increase in the zero shear viscosity as the gel point is approached as compared to the semibatch reactor resins. [ABSTRACT FROM AUTHOR]

of skin, comprises rigid corneocytes (keratin-filled dead cells) in a specialized lipid matrix. The continuous lipid matrix provides the main barrier against uncontrolled water loss and invasion of external pathogens. Unlike all other biological lipid membranes (such as intracellular organelles and plasma membranes), molecules in the SC lipid matrix show small hydrophilic groups and large variability in the length of the alkyl tails and in the numbers and positions of groups that are capable of forming hydrogen bonds. Molecular simulations provide a route for systematically probing the effects of each of these differences separately. In this article, we present the results fromatomistic molecular dynamics of selected lipid bilayers and multi-layers to probe the effect of these polydispersities. We address the nature of the tail packing in the gel-like phase, the hydrogen bond network among head groups, the bending moduli expected for leaflets comprising SC lipids and the conformation of very long ceramide lipids in multi-bilayer lipid assemblies. This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'. [ABSTRACT FROM AUTHOR]

[Display omitted] • "Nature-to-new" as a medicinal chemistry strategy. • Iterative Scaffold-hopping to identify new chemotype. • Organocatalysed Umpolung Chemistry to construct Arylidene heterocyclic-fused imidazolone scaffold. • Polyphosphoric acid-mediated ester-lactam exchange. • In silico study reveals good drug-like properties. A strategy of "Nature-to-new" with iterative scaffold-hopping was considered for investigation of privileged ring/functional motif-elaborated analogs of natural aurones. An organocatalyzed umpolung chemistry based method was established for molecular-diversity feasible synthesis of title class of chemotypes i.e. (Z)-2-Arylideneimidazo[1,2– a ]pyridinones and (Z)-2-Arylidenebenzo[ d ]imidazo[2,1–b]thiazol-3-ones. Various biophysical experiments indicated their important biological properties. The analogs showed characteristic anticancer activities with efficiency more than an anticancer drug. The compounds induced apoptosis with arrest in the S phase of the cell cycle regulation. The compounds' significant effect in up/down-regulation of various apoptotic proteins, an apoptosis cascade, and the inhibition of topoisomerases-mediated DNA relaxation process was identified. The analysis of the structure-activity relationship, interference with biological events and the drug-likeness physicochemical properties of the compounds in the acceptable window indicated distinctive medicinal molecule-to-properties of the investigated chemotypes. [ABSTRACT FROM AUTHOR]

In analogy with the pom-pom model, we introduce a simple model for comb polymers with multiple side-arms attached to a linear backbone by considering a set of coupled equations describing the stretch in the individual interbranch backbone segments. The stretch equations predict a sudden onset of backbone stretch as the flow rate is increased. Drag-strain coupling smooths this transition to some extent. For a series of well characterized polyisoprene and polystyrene combs, we find good agreement with the experimentally determined transient stress growth coefficients in uniaxial extension. [ABSTRACT FROM AUTHOR]

Copolymerization with nonconjugateddienes offers an attractiveroute for introducing long-chain branching in polypropylene. Froma simplified set of rate equations for such copolymerization witha metallocene catalyst, we derive the probabilities of branch formationat different stages of the reaction in a semibatch reactor. Usingthese probabilities, we generate an ensemble of molecules via a MonteCarlo sampling. The knowledge of the branching topology and segmentlengths allows us to compute the flow properties of the resins fromcomputational rheology. We compare our model predictions with existingexperimental data, namely the molar mass distribution and small amplitudeoscillatory shear response, for a set of resins with varying dienecontent. The rheology data suggest that the entanglement time τedepends sensitively and in a well-defined fashion on thediene content. [ABSTRACT FROM AUTHOR]

In a recent short communication [Read, D. J. et al., Science 333, 1871 (2011)], we showed that a computational scheme can describe the nonlinear flow properties for a series of industrial lowdensity polyethylene (LDPE) resins starting from the molecular architecture. The molecular architecture itself is determined by fitting parameters of a reaction kinetics model to average structural information obtained from gel-permeation chromatography and light scattering. Flow responses of these molecules in transient uniaxial extension and shear are calculated by mapping the stretch and orientation dynamics of the segments within the molecules to effective pom-pom modes. In this paper, we provide the details of the computational scheme and present additional results on a LDPE and a high-density polyethylene resin to illustrate the dependence of segmental maximum stretch variables on the flow rate. [ABSTRACT FROM AUTHOR]

The outermost layer of skin comprises rigid nonviable cells (corneocytes) in a layered lipid matrix. Using atomistic simulations we find that the equilibrium phase of the skin lipids is inverse micellar. A model of the corneocyte is used to demonstrate that lamellar layering is induced by the patterned corneocyte wall. The inverse micellar phase is consistent with in vivo observations in regions where corneocyte walls are well separated (lacunar spaces) and in the inner layers of skin, and suggests a functional role in the lipid synthesis pathway in vivo. [ABSTRACT FROM AUTHOR]

Hierarchical computational schemes based on tube theories enable calculation of rheological properties for polymers of arbitrary topology. In this study, such a scheme is used to systematically explore key rheological features of model long-chain branched systems. Empirical relations between molecular structure and rheology typically use overall molar mass and branching averages as structural variables, due to lack of knowledge on details of the topological structure or to limited structural variability between available experimental samples. The present approach clarifies the effect of additional structural variation beyond overall molar mass and branching level. For the polymer structures under consideration, arm length is found to dominate zero-shear viscosity, whereas the recoverable compliance scales with the ratio of total molar mass and backbone molar mass. Different topologies are found to lead to a different shear thinning/elasticity balance. The simulation approach provides clear hints for polymer designers that look to obtain specific property balances via topological modifications. This complements the classical empirical approach. Merging the different approaches is expected to synergistically speed up new product development. [ABSTRACT FROM AUTHOR]

We present a general algorithm for predicting the linear rheology of branched polymers. While the method draws heavily on existing theoretical understanding of the relaxation processes in entangled polymer melts, a number of new concepts are developed to handle diverse polymer architectures including branch-on-branch structures. We validate the algorithm with experimental examples from model polymer architectures to fix the parameters of the model. We use experimentally determined parameters to generate a numerical ensemble of branched metallocene-catalyzed polyethylene resins. Application of our algorithm shows the importance of branch-on-branch chains in the system and predicts the linear rheology with good quantitative agreement over a wide range of branching density and molecular weight. [ABSTRACT FROM AUTHOR]

In this work, we start with the quantum hydrodynamic model equations for two temperature-populated electrons in a dense plasma with quantum effects. We obtain the KdV equation for the electron acoustic (EAW) mode. The EAW self-interacts to form a rogue wave-type envelop soliton which is described by the nonlinear Schrodinger (NLS) equation. To study the stability criteria, we transform the KdV and NLS equations into its dynamical system counterparts and analyze the phase portraits and carry out the bifurcation analysis. The possibility of hyperchaos is discussed with reference to rogue waves. The finding will be helpful in laser plasma interactions, microelectronics, as well as beam plasma physics and fusion technology. [ABSTRACT FROM AUTHOR]

A semiconductor p-n junction diode with heavy doping under consideration is kept in forward biased condition. These are oppositely propagating electron and hole currents. These two streams interact among themselves and result in recombination, which supplies additional energy to the system. Such thermal energy creates additional electrical fluctuations, which exists long after the interaction has taken place. We have carried out an analytical investigation with numerical techniques as well as carried out a simulation of the wave–wave interaction in semiconductor junction diodes. In terms of signal transmission and operation of semiconductor device, such a theoretical study is important. [ABSTRACT FROM AUTHOR]

The flow response of branched entangled resins is dominated by the branching topology of the constituent molecules, a property that is not directly accessible using experimental analytical tools for industrially relevant complex resins. In this paper, the controlled terpolymerization of ethylene, 1,9‐decadiene, and either hexene or octene in a continuous stirred tank reactor with a metallocene catalyst, is reported. The synthesized samples are characterized extensively with various analytical tools and their rheological properties are measured with small amplitude oscillatory shear and start‐up uniaxial extension experiments. A model is developed for the polymerization process with the mass balance during synthesis providing strong constraints on the rate constants. In silico ensembles of molecules, generated via Monte Carlo sampling, are used to reproduce the experimental results. The computer model allows us to infer the detailed branching structure of the molecules and to predict the optimum range of reactor conditions for this synthesis. [ABSTRACT FROM AUTHOR]

In this paper, a novel seven-level Quasi-Z-Source-based T -type inverter (7L qZST 2 I) is proposed. The proposed inverter is an upgrade of Quasi-Z-source (qZs) network and seven-level T -type inverter. The 7L qZST 2 I comprises of three qZs-based impedance networks, two bidirectional switches and an H -bridge inverter. It owns the advantages of reduced switch count, improved output voltage gain, enhanced reliability and better quality of output voltage and current. The performance of the proposed topology is tested for two different pulse width modulation techniques based on shoot-through control. The first technique offers simple control and operated at a fixed shoot-through duty cycle for realizing output voltage level. The second technique facilitates independent control of each qZs network dc-link voltage and they can be operated at different shoot through duty cycle which overcomes the limitation of first technique with better quality in output voltage. The detailed operation of the proposed topology and control schemes have been elaborated for different switching states for each output voltage level generation. Extensive simulation and experimentation are performed for both the switching schemes to verify their performance under steady state and dynamic conditions. Furthermore, a brief comparison is constructed to highlight the merits of the proposed inverter with conventional topologies. [ABSTRACT FROM AUTHOR]

In this work, the nonlinear KdV solitary structures have been studied in electron acoustic waves in a thermal magnetoplasma with Kappa-distributed ions by employing a reductive perturbation technique. Relativistic streaming effects are also incorporated. External forcing term on the KdV soliton is studied via the forced KdV equation. Further nonlinear self-interactions have been studied through the nonlinear Schrödinger equation. Dynamical systems have been studied and the parametric phase portraits are graphically analyzed. The results will be helpful in the laboratory plasmas where magnetic confinement is employed. High-energy plasma at greater density can be studied with our model problem. [ABSTRACT FROM AUTHOR]

Bifurcation analysis and dynamical system studies are carried out to find the stability regime and chaotic scenario in electron acoustic waves in relativistic degenerate plasma. We have obtained the quantum hydrodynamic model and obtain the Korteweg–de Vries equation describing the nature and characteristics of solitary structures. The amplitude modulated envelop soliton formation due to external perturbations has been studied by analyzing the nonlinear Schrodinger equation. Further to study the stability factors and the parametric range for such stability, the dynamical system is studied and bifurcation analysis has been carried out. The chaotic behavior of the system is studied through largest Lyapunov exponent (LLE). This work will find application in theoretically predicting the stable modes in many solar plasma and stellar plasma applications and in laser plasma in future. [ABSTRACT FROM AUTHOR]

In this work, we start with the ion-acoustic waves in galactic plasma with the degenerate matter. We use the reductive perturbation technique to derive the spherical Kadomtsev–Petviashvili (SKP) equation. We next employ homotopy-aided symbolic simulation (HASS) to study the evolution of the spherical solitary wavefront. We compare the results obtained by HPM and RPT. To understand how the system behaves, we transform the evolutionary equations into a dynamical system. The phase portraits and the superperiodic waves reflect on the intricate processes within the plasma and determine the stability criteria and possible situations of chaos. The work will find applications in many astrophysical observations, such as electrostatic wave modes, gamma-ray bursts, and double-layer solitons. PACS—95.30.Qd, 52.65.-y, 52.35.-g, 52.35.Tc. [ABSTRACT FROM AUTHOR]

In this article, we have studied the electron acoustic waves in a magnetized plasma containing Kappa distributed ions which are streaming with high velocity within the plasma and under the action of external force. We employed the homotopy perturbation method (HPM) to obtain the graphical plots of solitary structures and their evolution into an envelope soliton. Analytically, we obtained the linear dispersion relation and studied its characteristics. Further, we derived the Korteweg–De Vries (KdV) equation using the reductive perturbation technique and studied the parametric dependence on the KdV solitary profile. These findings augment the homotopy results. The analytical and simulation results thus obtained will be helpful in interpretating and identifying electron acoustic wave (EAW) modes in such a plasma system. [ABSTRACT FROM AUTHOR]

By employing a quantum hydrodynamic (QHD) model with appropriate boundary conditions, the nonlinear self-interaction of an electrostatic surface wave on otherwise homogeneous semibounded plasma with degeneracy effects is investigated. It has been found that a part of the second harmonic generated through self-interaction does not have a true surface wave feature but propagates obliquely away from the plasma–vacuum interface into the bulk of the plasma. Such a situation is obtained in laser–plasma interaction during surface etching, plasma processing, and so on. In this article, we study the harmonics generation mechanism, associated Lagrangian chaos, and harmonic conversation rate when an intense laser is incident on an unmagnetized plasma. The dense plasma displays quantum diffraction effects and other quantum statistical effects. We made use of perturbative analysis for the field quantities. The findings will help workers dealing with laser–plasma interaction so as to enhance the tendency of harmonic generation and energy localization. [ABSTRACT FROM AUTHOR]

We present a predictive scheme connecting the topological structure of highly branched entangled polymers, with industrial-level complexity, to the emergent viscoelasticity of the polymer melt. The scheme is able to calculate the linear and nonlinear viscoelasticity of a stochastically branched "high-pressure free radical" polymer melt as a function of the chemical kinetics of its formation. The method combines numerical simulation of polymerization with the tube/ entanglement physics of polymer dynamics extended to fully nonlinear response. We compare calculations for a series of low-density polyethylenes with experiments on structural and viscoelastic properties. The method provides a window onto the molecular processes responsible for the optimized rheology of these melts, connecting fundamental science to process in complex flow, and opens up the in silico design of new materials. [ABSTRACT FROM AUTHOR]

We develop a thermodynamic continuum-level model, polySTRAND, for flow-induced nucleation in polymers suitable for use in computational process modeling. The model's molecular origins ensure that it accounts properly for flow and nucleation dynamics of polydisperse systems and can be extended to include effects of exhaustion of highly deformed chains and nucleus roughness. It captures variations with the key processing parameters, flow rate, temperature, and molecular weight distribution. Under strong flow, long chains are over-represented within the nucleus, leading to superexponential nucleation rate growth with shear rate as seen in experiments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Systematic investigation of the linear and nonlinear shear rheology of a well-characterized moderately entangled H-polystyrene having branches and backbone of nearly the same molar mass. The polymer is checked to be structurally pure via TGIC. • The nonlinear shear experiments are performed with state-of-the-art rheometry using the cone-partitioned plate fixture. • The BoB model describes the linear viscoelasticity as well as the nonlinear start-up shear response, with overshoot and steady state, at lower shear rates. • The presented dataset is useful for further analysis and comparisons in the direction of extending the BoB model by including finite extensibility effects. We present a systematic investigation of the linear viscoelasticity and nonlinear start-up shear flow response of a well-characterized H-polystyrene, an archetype branched polymer. The Branch-on-Branch (BoB) model describes the linear response well, as well as the nonlinear transient response at lower rates, in the regime where finite extensibility effects do not seem to be important. The data reveal shear thinning similar to that of comb polymers and a broad transient overshoot of the shear stress growth coefficient, which suggests a coupled response of backbone and branches. The rich features of the data and comparison with the BoB-model should provide a useful framework for further exploring the transient molecular response of branched polymers in complex flows. [ABSTRACT FROM AUTHOR]

Although sensitization of BRCA-mutated, homologous recombination (HR)-deficient breast cancer cells through PARP inhibitor is widely studied, not much is known about the treatment of BRCA-wild-type, HR-proficient breast cancer. Here, we aim to investigate whether a bioactive compound, Resveratrol (RES), can induce DNA double-strand breaks in HR-proficient breast cancer cells and Olaparib (OLA), a PARP inhibitor, can enhance the RES-mediated apoptosis by deregulating the HR repair pathway. The detailed mechanism of anti-cancer action of RES + OLA combination in breast cancer has been evaluated using in vitro , ex vivo , and in vivo preclinical model systems. OLA increased RES-mediated DNA damage, downregulated the HR pathway proteins, caused a late S/G2 cell cycle arrest, enhanced apoptosis and cell death in RES pre-treated breast cancer cells at much lower concentrations than their individual treatments. Direct measurement of HR pathway activity using a GFP plasmid-based assay demonstrated reduced HR efficiency in I-SceI endonuclease-transfected cells treated with OLA. Moreover, RES + OLA treatment also caused significant reduction in PARP1-mediated PARylation and efficiently trapped PARP1 at the DNA damage site. Upon RES treatment, PARylated PARP1 was found to interact with BRCA1, which then activated other HR pathway proteins. But after addition of OLA in RES pre-treated cells, PARP1 could not interact with BRCA1 due to inhibition of PARylation. This resulted in deregulation of HR pathway. To further confirm the role of BRCA1 in PARP1-mediated HR pathway activation, BRCA1 was knocked down that caused complete inhibition of HR pathway activity, and further enhanced apoptosis after RES + OLA treatment in BRCA1-silenced cells. In agreement with in vitro data, similar experimental results were obtained in ex vivo patient-derived breast cancer cells and in vivo xenograft mice. Thus, RES + OLA combination treatment enhanced breast cancer cell death by causing excessive DNA damage and also simultaneously inhibiting the HR pathway. (1) Exposure of cancer cells to the DNA damaging agent, Resveratrol (RES), causes a double-stranded break (DSB) within the DNA molecule. (2) Activation of PARP1 and PARP1-mediated PARylation take place at the DNA damage site. (3) PARylated PARP1 interacts with BRCA1 and induces activation of HR pathway proteins (MRN complex, RPA70, BRCA2, RAD51, etc.) by forming a PAR chain around the HR protein complex. (4) Auto-PARylation of PARP-1 results in dissociation of PARP-1 from the HR complex resulting in full progression of HR repair. (5) Successful and error-free repair of the DSB by HR cascade leads to cancer cell survival. (6) When RES-treated breast cancer cells are exposed to Olaparib (OLA), the functions of PARP1 are inhibited by PARP1-trapping at the DNA damage site. Inhibition of PARP1-mediated PARylation terminates the interaction between PARP1 and BRCA1. (7) This causes inactivation of HR pathway proteins and cessation of the HR pathway. (8) HR pathway inhibition leads to accumulation of DSBs in and around the DNA damage site. (9) This results in cell cycle arrest, apoptosis, and cancer cell death (Created with BioRender.com). Olaparib enhances Resveratrol-mediated apoptosis in breast cancer cells by inhibiting the homologous recombination repair pathway. [Display omitted] • Olaparib enhanced the resveratrol-induced cytotoxicity in breast cancer cells. • Olaparib inhibited PARylation, and blocked PARP1-BRCA1 interaction. • HR pathway inhibition led to cell cycle arrest and apoptosis of the cancer cells. • Results were confirmed in patient-derived breast cancer cells and xenograft mice. [ABSTRACT FROM AUTHOR]

Relaxation of branched polymers undertube-based models involvesa parameter p2characterizing the hopsize of relaxed side arms. Depending on assumptions made in rheologicalmodels (e.g., about the relevant tube diameter for branch-point hops), p2had been set to values varying from 1 to 1/60in the literature. From large-scale molecular dynamics simulationsof melts of entangled branched polymers of different architectures,and from experimental rheological data on a set of well-characterizedcomb polymers with many (∼30) side arms, we estimate the valuesof p2under different assumptions in thehierarchical relaxation scheme. Both the simulations and the experimentsshow that including the backbone friction and considering hoppingin the dilated tube provides the most consistent set of hopping parametersin different architectures. [ABSTRACT FROM AUTHOR]