Nonlinearly stacked low noise turbofan stator
NASA Technical Reports Server (NTRS)
Schuster, William B. (Inventor); Kontos, Karen B. (Inventor); Weir, Donald S. (Inventor); Nolcheff, Nick A. (Inventor); Gunaraj, John A. (Inventor)
2009-01-01
A nonlinearly stacked low noise turbofan stator vane having a characteristic curve that is characterized by a nonlinear sweep and a nonlinear lean is provided. The stator is in an axial fan or compressor turbomachinery stage that is comprised of a collection of vanes whose highly three-dimensional shape is selected to reduce rotor-stator and rotor-strut interaction noise while maintaining the aerodynamic and mechanical performance of the vane. The nonlinearly stacked low noise turbofan stator vane reduces noise associated with the fan stage of turbomachinery to improve environmental compatibility.
Nonlinear acoustic impedance of thermoacoustic stack
NASA Astrophysics Data System (ADS)
Ge, Huan; Fan, Li; Xiao, Shu-yu; Tao, Sha; Qiu, Mei-chen; Zhang, Shu-yi; Zhang, Hui
2012-09-01
In order to optimize the performances of the thermoacoustic refrigerator working with the high sound pressure level, the nonlinear acoustic characteristics of the thermoacoustic stack in the resonant pipe are studied. The acoustic fluid impedance of the stack made of copper mesh and set up in a resonant pipe is measured in the acoustic fields with different intensities. It is found that when the sound pressure level in the pipe increases to a critical value, the resistance of the stack increases nonlinearly with the sound pressure, while the reactance of the stack keeps constant. Based on the experimental results, a theory model is set up to describe the acoustic characteristics of the stack, according to the rigid frame theory and Forchheimmer equation. Furthermore, the influences of the sound pressure level, operating frequency, volume porosity, and length of the stack on the nonlinear impedance of the stack are evaluated.
Stacking interactions and DNA intercalation
Li, Dr. Shen; Cooper, Valentino R; Thonhauser, Prof. Timo; Lundqvist, Prof. Bengt I.; Langreth, David C.
2009-01-01
The relationship between stacking interactions and the intercalation of proflavine and ellipticine within DNA is investigated using a nonempirical van der Waals density functional for the correlation energy. Our results, employing a binary stack model, highlight fundamental, qualitative differences between base-pair base-pair interactions and that of the stacked intercalator base pair system. Most notable result is the paucity of torque which so distinctively defines the Twist of DNA. Surprisingly, this model, when combined with a constraint on the twist of the surrounding base-pair steps to match the observed unwinding of the sugar-phosphate backbone, was sufficient for explaining the experimentally observed proflavine intercalator configuration. Our extensive mapping of the potential energy surface of base-pair intercalator interactions can provide valuable information for future nonempirical studies of DNA intercalation dynamics.
Nonlinear dynamics of a stack/cable system
Cai, Y.; Chen, S.S.
1995-07-01
In this study, we developed a coupled model of wind-induced vibration of a stack, based on an unsteady-flow theory and nonlinear dynamics of the stack`s heavy elastic suspended cables. Numerical analysis was performed to identify excitation mechanisms. The stack was found to be excited by vortex shedding. Once lock-in resonance occurred, the cables were excited by the transverse motion of the stack. Large-amplitude oscillations of the cables were due to parametric resonance. Appropriate techniques have been proposed to alleviate the vibration problem.
Stacking interactions in PUF-RNA complexes
Yiling Koh, Yvonne; Wang, Yeming; Qiu, Chen; Opperman, Laura; Gross, Leah; Tanaka Hall, Traci M; Wickens, Marvin
2012-07-02
Stacking interactions between amino acids and bases are common in RNA-protein interactions. Many proteins that regulate mRNAs interact with single-stranded RNA elements in the 3' UTR (3'-untranslated region) of their targets. PUF proteins are exemplary. Here we focus on complexes formed between a Caenorhabditis elegans PUF protein, FBF, and its cognate RNAs. Stacking interactions are particularly prominent and involve every RNA base in the recognition element. To assess the contribution of stacking interactions to formation of the RNA-protein complex, we combine in vivo selection experiments with site-directed mutagenesis, biochemistry, and structural analysis. Our results reveal that the identities of stacking amino acids in FBF affect both the affinity and specificity of the RNA-protein interaction. Substitutions in amino acid side chains can restrict or broaden RNA specificity. We conclude that the identities of stacking residues are important in achieving the natural specificities of PUF proteins. Similarly, in PUF proteins engineered to bind new RNA sequences, the identity of stacking residues may contribute to 'target' versus 'off-target' interactions, and thus be an important consideration in the design of proteins with new specificities.
Nonlinear dynamics of a stack/cable system subjected to vortex-induced vibration
Cai, Y.; Chen, S.S.
1995-12-31
A model of a stack/wire system, wind-induced vibration of the stack based on an unsteady-flow theory, and nonlinear dynamics of the stack`s heavy elastic suspended cables was developed in this study. The response characteristics of the stack and cables are presented for different conditions. The dominant excitation mechanisms are lock-in resonance of the stack by vortex shedding and parametric resonance of suspended cables by stack motion at their support ends.
Nonlinear dynamics of a stack/cable system subjected to vortex-induced vibration
Cai, Y.; Chen, S.S.
1997-08-01
A model of a stack/wire system, wind-induced vibration of the stack based on an unsteady-flow theory, and nonlinear dynamics of the stack`s heavy elastic suspended cables was developed in this study. The response characteristics of the stack and cables are presented for different conditions. The dominant excitation mechanisms are lock-in resonance of the stack by vortex shedding and parametric resonance of suspended cables by stack motion at their support ends.
NASA Astrophysics Data System (ADS)
Barus, R. P. P.; Tjokronegoro, H. A.; Leksono, E.; Ismunandar
2014-09-01
Fuel cells are promising new energy conversion devices that are friendly to the environment. A set of control systems are required in order to operate a fuel cell based power plant system optimally. For the purpose of control system design, an accurate fuel cell stack model in describing the dynamics of the real system is needed. Currently, linear model are widely used for fuel cell stack control purposes, but it has limitations in narrow operation range. While nonlinear models lead to nonlinear control implemnetation whos more complex and hard computing. In this research, nonlinear cancellation technique will be used to transform a nonlinear model into a linear form while maintaining the nonlinear characteristics. The transformation is done by replacing the input of the original model by a certain virtual input that has nonlinear relationship with the original input. Then the equality of the two models is tested by running a series of simulation. Input variation of H2, O2 and H2O as well as disturbance input I (current load) are studied by simulation. The error of comparison between the proposed model and the original nonlinear model are less than 1 %. Thus we can conclude that nonlinear cancellation technique can be used to represent fuel cell nonlinear model in a simple linear form while maintaining the nonlinear characteristics and therefore retain the wide operation range.
Barus, R. P. P.; Tjokronegoro, H. A.; Leksono, E.; Ismunandar
2014-09-25
Fuel cells are promising new energy conversion devices that are friendly to the environment. A set of control systems are required in order to operate a fuel cell based power plant system optimally. For the purpose of control system design, an accurate fuel cell stack model in describing the dynamics of the real system is needed. Currently, linear model are widely used for fuel cell stack control purposes, but it has limitations in narrow operation range. While nonlinear models lead to nonlinear control implemnetation whos more complex and hard computing. In this research, nonlinear cancellation technique will be used to transform a nonlinear model into a linear form while maintaining the nonlinear characteristics. The transformation is done by replacing the input of the original model by a certain virtual input that has nonlinear relationship with the original input. Then the equality of the two models is tested by running a series of simulation. Input variation of H2, O2 and H2O as well as disturbance input I (current load) are studied by simulation. The error of comparison between the proposed model and the original nonlinear model are less than 1 %. Thus we can conclude that nonlinear cancellation technique can be used to represent fuel cell nonlinear model in a simple linear form while maintaining the nonlinear characteristics and therefore retain the wide operation range.
Twist versus nonlinear stacking in short DNA molecules.
Zoli, Marco
2014-08-01
The denaturation of the double helix is a template for fundamental biological functions such as replication and transcription involving the formation of local fluctuational openings. The denaturation transition is studied for heterogeneous short sequences of DNA, i.e. ~100 base pairs, in the framework of a mesoscopic Hamiltonian model which accounts for the helicoidal geometry of the molecule. The theoretical background for the application of the path integral formalism to predictive analysis of the molecule thermodynamical properties is discussed. The base pair displacements with respect to the ground state are treated as paths whose temperature dependent amplitudes are governed by the thermal wavelength. The ensemble of base pairs paths is selected, at any temperature, consistently with both the model potential and the second law of thermodynamics. The partition function incorporates the effects of the base pair thermal fluctuations which become stronger close to the denaturation. The transition appears as a gradual phenomenon starting from the molecule segments rich in adenine-thymine base pairs. Computing the equilibrium thermodynamics, we focus on the interplay between twisting of the complementary strands around the molecule axis and nonlinear stacking potential: it is shown that the latter affects the melting profiles only if the rotational degrees of freedom are included in the Hamiltonian. The use of ladder Hamiltonian models for the DNA complementary strands in the pre-melting regime is questioned. PMID:24685891
Nonlinear interaction between single photons.
Guerreiro, T; Martin, A; Sanguinetti, B; Pelc, J S; Langrock, C; Fejer, M M; Gisin, N; Zbinden, H; Sangouard, N; Thew, R T
2014-10-24
Harnessing nonlinearities strong enough to allow single photons to interact with one another is not only a fascinating challenge but also central to numerous advanced applications in quantum information science. Here we report the nonlinear interaction between two single photons. Each photon is generated in independent parametric down-conversion sources. They are subsequently combined in a nonlinear waveguide where they are converted into a single photon of higher energy by the process of sum-frequency generation. Our approach results in the direct generation of photon triplets. More generally, it highlights the potential for quantum nonlinear optics with integrated devices and, as the photons are at telecom wavelengths, it opens the way towards novel applications in quantum communication such as device-independent quantum key distribution. PMID:25379916
Scalora, Michael; Mattiucci, Nadia; D'Aguanno, Giuseppe; Larciprete, MariaCristina; Bloemer, Mark J
2006-01-01
We numerically study the nonlinear optical properties of metal-dielectric photonic band gap structures in the pulsed regime. We exploit the high chi3 of copper metal to induce nonlinear effects such as broadband optical limiting, self-phase modulation, and unusual spectral narrowing of high intensity pulses. We show that in a single pass through a typical, chirped multilayer stack nonlinear transmittance and peak powers can be reduced by nearly two orders of magnitude compared to low light intensity levels across the entire visible range. Chirping dielectric layer thickness dramatically improves the linear transmittance through the stack and achieves large fields inside the copper to access the large nonlinearity. At the same time, the linear properties of the stack block most of the remaining electromagnetic spectrum. PMID:16486291
Interaction: Additivity plus Nonlinearity?
ERIC Educational Resources Information Center
Hutchinson, T. P.
2004-01-01
Whether or not there is an interaction between two factors in their effects on a dependent variable is often a central question. This paper proposes a general mechanism by which an interaction may arise: (a) the two factors are the same thing--or, at least, have a dimension in common--in the sense that it is meaningful to add (or subtract) them;…
Edge-edge interactions in stacked graphene nanoplatelets
Cruz Silva, Eduardo; Terrones Maldonado, Humberto; Terrones Maldonado, Mauricio; Jia, Xiaoting; Sumpter, Bobby G; Dresselhaus, M; Meunier, V.
2013-01-01
High-resolution transmission electron microscopy (HRTEM) studies show the dynamics of small graphene platelets on larger graphene layers. The platelets move nearly freely to eventually lock in at well-defined positions close to the edges of the larger underlying graphene sheet. While such movement is driven by a shallow potential energy surface described by an interplane interaction, the lock-in position occurs by via edge-edge interactions of the platelet and the graphene surface located underneath. Here we quantitatively study this behavior using van der Waals density functional calculations. Local interactions at the open edges are found to dictate stacking configurations that are different from Bernal (AB) stacking. These stacking configurations are known to be otherwise absent in edge-free two-dimensional (2D) graphene. The results explain the experimentally observed platelet dynamics and provide a detailed account of the new electronic properties of these combined systems.
Interaction driven quantum Hall effect in artificially stacked graphene bilayers.
Iqbal, Muhammad Zahir; Iqbal, Muhammad Waqas; Siddique, Salma; Khan, Muhammad Farooq; Ramay, Shahid Mahmood; Nam, Jungtae; Kim, Keun Soo; Eom, Jonghwa
2016-01-01
The honeycomb lattice structure of graphene gives rise to its exceptional electronic properties of linear dispersion relation and its chiral nature of charge carriers. The exceptional electronic properties of graphene stem from linear dispersion relation and chiral nature of charge carries, originating from its honeycomb lattice structure. Here, we address the quantum Hall effect in artificially stacked graphene bilayers and single layer graphene grown by chemical vapor deposition. The quantum Hall plateaus started to appear more than 3 T and became clearer at higher magnetic fields up to 9 T. Shubnikov-de Hass oscillations were manifestly observed in graphene bilayers texture. These unusual plateaus may have been due to the layers interaction in artificially stacked graphene bilayers. Our study initiates the understanding of interactions between artificially stacked graphene layers. PMID:27098387
Interaction driven quantum Hall effect in artificially stacked graphene bilayers
Iqbal, Muhammad Zahir; Iqbal, Muhammad Waqas; Siddique, Salma; Khan, Muhammad Farooq; Ramay, Shahid Mahmood; Nam, Jungtae; Kim, Keun Soo; Eom, Jonghwa
2016-01-01
The honeycomb lattice structure of graphene gives rise to its exceptional electronic properties of linear dispersion relation and its chiral nature of charge carriers. The exceptional electronic properties of graphene stem from linear dispersion relation and chiral nature of charge carries, originating from its honeycomb lattice structure. Here, we address the quantum Hall effect in artificially stacked graphene bilayers and single layer graphene grown by chemical vapor deposition. The quantum Hall plateaus started to appear more than 3 T and became clearer at higher magnetic fields up to 9 T. Shubnikov-de Hass oscillations were manifestly observed in graphene bilayers texture. These unusual plateaus may have been due to the layers interaction in artificially stacked graphene bilayers. Our study initiates the understanding of interactions between artificially stacked graphene layers. PMID:27098387
Interaction driven quantum Hall effect in artificially stacked graphene bilayers
NASA Astrophysics Data System (ADS)
Iqbal, Muhammad Zahir; Iqbal, Muhammad Waqas; Siddique, Salma; Khan, Muhammad Farooq; Ramay, Shahid Mahmood; Nam, Jungtae; Kim, Keun Soo; Eom, Jonghwa
2016-04-01
The honeycomb lattice structure of graphene gives rise to its exceptional electronic properties of linear dispersion relation and its chiral nature of charge carriers. The exceptional electronic properties of graphene stem from linear dispersion relation and chiral nature of charge carries, originating from its honeycomb lattice structure. Here, we address the quantum Hall effect in artificially stacked graphene bilayers and single layer graphene grown by chemical vapor deposition. The quantum Hall plateaus started to appear more than 3 T and became clearer at higher magnetic fields up to 9 T. Shubnikov-de Hass oscillations were manifestly observed in graphene bilayers texture. These unusual plateaus may have been due to the layers interaction in artificially stacked graphene bilayers. Our study initiates the understanding of interactions between artificially stacked graphene layers.
Aromatic stacking interactions govern catalysis in aryl-alcohol oxidase.
Ferreira, Patricia; Hernández-Ortega, Aitor; Lucas, Fátima; Carro, Juan; Herguedas, Beatriz; Borrelli, Kenneth W; Guallar, Victor; Martínez, Angel T; Medina, Milagros
2015-08-01
Aryl-alcohol oxidase (AAO, EC 1.1.3.7) generates H2 O2 for lignin degradation at the expense of benzylic and other π system-containing primary alcohols, which are oxidized to the corresponding aldehydes. Ligand diffusion studies on Pleurotus eryngii AAO showed a T-shaped stacking interaction between the Tyr92 side chain and the alcohol substrate at the catalytically competent position for concerted hydride and proton transfers. Bi-substrate kinetics analysis revealed that reactions with 3-chloro- or 3-fluorobenzyl alcohols (halogen substituents) proceed via a ping-pong mechanism. However, mono- and dimethoxylated substituents (in 4-methoxybenzyl and 3,4-dimethoxybenzyl alcohols) altered the mechanism and a ternary complex was formed. Electron-withdrawing substituents resulted in lower quantum mechanics stacking energies between aldehyde and the tyrosine side chain, contributing to product release, in agreement with the ping-pong mechanism observed in 3-chloro- and 3-fluorobenzyl alcohol kinetics analysis. In contrast, the higher stacking energies when electron donor substituents are present result in reaction of O2 with the flavin through a ternary complex, in agreement with the kinetics of methoxylated alcohols. The contribution of Tyr92 to the AAO reaction mechanism was investigated by calculation of stacking interaction energies and site-directed mutagenesis. Replacement of Tyr92 by phenylalanine does not alter the AAO kinetic constants (on 4-methoxybenzyl alcohol), most probably because the stacking interaction is still possible. However, introduction of a tryptophan residue at this position strongly reduced the affinity for the substrate (i.e. the pre-steady state Kd and steady-state Km increase by 150-fold and 75-fold, respectively), and therefore the steady-state catalytic efficiency, suggesting that proper stacking is impossible with this bulky residue. The above results confirm the role of Tyr92 in substrate binding, thus governing the kinetic mechanism
New Insights into Hydrogen Bonding and Stacking Interactions in Cellulose
Langan, Paul
2011-01-01
In this quantum chemical study, we explore hydrogen bonding (H-bonding) and stacking interactions in different crystalline cellulose allomorphs, namely cellulose I and cellulose IIII. We consider a model system representing a cellulose crystalline core, made from six cellobiose units arranged in three layers with two chains per layer. We calculate the contributions of intrasheet and intersheet interactions to the structure and stability in both cellulose I and cellulose IIII crystalline cores. Reference structures for this study were generated from molecular dynamics simulations of water-solvated cellulose I and IIII fibrils. A systematic analysis of various conformations describing different mutual orientations of cellobiose units is performed using the hybrid density functional theory (DFT) with the M06-2X with 6-31+G (d, p) basis sets. We dissect the nature of the forces that stabilize the cellulose I and cellulose IIII crystalline cores and quantify the relative strength of H-bonding and stacking interactions. Our calculations demonstrate that individual H-bonding interactions are stronger in cellulose I than in cellulose IIII. We also observe a significant contribution from cooperative stacking interactions to the stabilization of cellulose I . In addition, the theory of atoms-in-molecules (AIM) has been employed to characterize and quantify these intermolecular interactions. AIM analyses highlight the role of nonconventional CH O H-bonding in the cellulose assemblies. Finally, we calculate molecular electrostatic potential maps for the cellulose allomorphs that capture the differences in chemical reactivity of the systems considered in our study.
Stacked stem cell sheets enhance cell-matrix interactions
Patel, Nikul G; Zhang, Ge
2014-01-01
Cell sheet engineering has enabled the production of confluent cell sheets stacked together for use as a cardiac patch to increase cell survival rate and engraftment after transplantation, thereby providing a promising strategy for high density stem cell delivery for cardiac repair. One key challenge in using cell sheet technology is the difficulty of cell sheet handling due to its weak mechanical properties. A single-layer cell sheet is generally very fragile and tends to break or clump during harvest. Effective transfer and stacking methods are needed to move cell sheet technology into widespread clinical applications. In this study, we developed a simple and effective micropipette based method to aid cell sheet transfer and stacking. The cell viability after transfer was tested and multi-layer stem cell sheets were fabricated using the developed method. Furthermore, we examined the interactions between stacked stem cell sheets and fibrin matrix. Our results have shown that the preserved ECM associated with the detached cell sheet greatly facilitates its adherence to fibrin matrix and enhances the cell sheet-matrix interactions. Accelerated fibrin degradation caused by attached cell sheets was also observed. PMID:24769850
Interaction nonlinearity in asphalt binders
NASA Astrophysics Data System (ADS)
Motamed, Arash; Bhasin, Amit; Liechti, Kenneth M.
2012-05-01
Asphalt mixtures are complex composites that comprise aggregate, asphalt binder, and air. Several research studies have shown that the mechanical behavior of the asphalt mixture is strongly influenced by the matrix, i.e. the asphalt binder. Characterization and a thorough understanding of the binder behavior is the first and crucial step towards developing an accurate constitutive model for the composite. Accurate constitutive models for the constituent materials are critical to ensure accurate performance predictions at a material and structural level using micromechanics. This paper presents the findings from a systematic investigation into the nature of the linear and nonlinear response of asphalt binders subjected to different types of loading using the Dynamic Shear Rheometer (DSR). Laboratory test data show that a compressive normal force is generated in an axially constrained specimen subjected to torsional shear. This paper investigates the source of this normal force and demonstrates that the asphalt binder can dilate when subjected to shear loads. This paper also presents the findings from a study conducted to investigate the source of the nonlinearity in the asphalt binder. Test results demonstrate that the application of cyclic shear loads results in the development of a normal force and a concomitant reduction in the dynamic shear modulus. This form of nonlinear response is referred to as an "interaction nonlinearity". A combination of experimental and analytical tools is used to demonstrate and verify the presence of this interaction nonlinearity in asphalt binders. The findings from this study highlight the importance of modeling the mechanical behavior of asphalt binders based on the overall stress state of the material.
Atomic-scale details of dislocation - stacking fault tetrahedra interaction.
Osetskiy, Yury N; Stoller, Roger E; Rodney, David; Bacon, David J
2005-01-01
Stacking fault tetrahedra (SFTs) are formed during irradiation of fcc. metals and alloys with low stacking fault energy. The high number density of SFTs observed suggests that they should contribute to radiation-induced hardening and, therefore, be taken into account when estimating mechanical property changes of irradiated materials. The key issue is to describe the interaction between a moving dislocation and an individual SFT, which is characterized by a small physical scale of about 100 nm. In this paper we present results of an atomistic simulation of edge and screw dislocations interacting with small SFTs at different temperatures and strain rates and present mechanisms which can explain the formation of defect-free channels observed experimentally.
Interactive histology of large-scale biomedical image stacks.
Jeong, Won-Ki; Schneider, Jens; Turney, Stephen G; Faulkner-Jones, Beverly E; Meyer, Dominik; Westermann, Rüdiger; Reid, R Clay; Lichtman, Jeff; Pfister, Hanspeter
2010-01-01
Histology is the study of the structure of biological tissue using microscopy techniques. As digital imaging technology advances, high resolution microscopy of large tissue volumes is becoming feasible; however, new interactive tools are needed to explore and analyze the enormous datasets. In this paper we present a visualization framework that specifically targets interactive examination of arbitrarily large image stacks. Our framework is built upon two core techniques: display-aware processing and GPU-accelerated texture compression. With display-aware processing, only the currently visible image tiles are fetched and aligned on-the-fly, reducing memory bandwidth and minimizing the need for time-consuming global pre-processing. Our novel texture compression scheme for GPUs is tailored for quick browsing of image stacks. We evaluate the usability of our viewer for two histology applications: digital pathology and visualization of neural structure at nanoscale-resolution in serial electron micrographs. PMID:20975179
The influence of piezoceramic stack location on nonlinear behavior of Langevin transducers.
Mathieson, Andrew; Cardoni, Andrea; Cerisola, Niccolò; Lucas, Margaret
2013-06-01
Power ultrasonic applications such as cutting, welding, and sonochemistry often use Langevin transducers to generate power ultrasound. Traditionally, it has been proposed that the piezoceramic stack of a Langevin transducer should be located in the nodal plane of the longitudinal mode of vibration, ensuring that the piezoceramic elements are positioned under a uniform stress during transducer operation, maximizing element efficiency and minimizing piezoceramic aging. However, this general design rule is often partially broken during the design phase if features such as a support flange or multiple piezoceramic stacks are incorporated into the transducer architecture. Meanwhile, it has also been well documented in the literature that power ultrasonic devices driven at high excitation levels exhibit nonlinear behaviors similar to those observed in Duffing-type systems, such as resonant frequency shifts, the jump phenomenon, and hysteretic regions. This study investigates three Langevin transducers with different piezoceramic stack locations by characterizing their linear and nonlinear vibrational responses to understand how the stack location influences nonlinear behavior. PMID:25004475
RKKY interaction in AB-stacked multilayer graphene
NASA Astrophysics Data System (ADS)
Jiang, Liwei; Lü, Xiaoling; Gao, Wenzhu; Yu, Guodong; Liu, Zhe; Zheng, Yisong
2012-05-01
The RKKY interaction between two magnetic impurities absorbed on the surface layer of half-filled AB-stacked multilayer graphene (ABSMLG) is theoretically studied based on the lattice Green’s function technique. In comparison with the case of monolayer graphene, the RKKY interaction in such multilayer graphene presents distinct properties in some aspects. Firstly, from the numerical results, we find that the thickness of the ABSMLG influences the RKKY interaction in a complicated manner, depending on the odd/even parity of the number of layers and the sublattice attribution of the positions of the two magnetic impurities. Then, we derive the asymptotic expressions of the RKKY interactions in ABSMLG in the long-distance limit. For even-layered ABSMLG, we find that the RKKY interactions of the 1A-1A, 1B-1A and 1B-1B couplings fall off as 1/R2, 1/R4 and 1/R6 (1A and 1B stand for, respectively, the sublattice points in the surface layer, which are positioned directly on the plaquette and on a lattice point of the layer underneath). On the other hand, in odd-layered ABSMLG, the decays of these interactions follow the 1/R2, 1/R3 and 1/R3 power laws respectively. In addition, we also find that these analytical expressions are quantitatively valid to describe the RKKY interaction in ABSMLG when the distance between the two magnetic impurities is larger than the lattice constant of graphene by one order of magnitude.
A nonlinear dynamic model of DNA with a sequence-dependent stacking term
Alexandrov, Boian S.; Gelev, Vladimir; Monisova, Yevgeniya; Alexandrov, Ludmil B.; Bishop, Alan R.; Rasmussen, Kim Ø.; Usheva, Anny
2009-01-01
No simple model exists that accurately describes the melting behavior and breathing dynamics of double-stranded DNA as a function of nucleotide sequence. This is especially true for homogenous and periodic DNA sequences, which exhibit large deviations in melting temperature from predictions made by additive thermodynamic contributions. Currently, no method exists for analysis of the DNA breathing dynamics of repeats and of highly G/C- or A/T-rich regions, even though such sequences are widespread in vertebrate genomes. Here, we extend the nonlinear Peyrard–Bishop–Dauxois (PBD) model of DNA to include a sequence-dependent stacking term, resulting in a model that can accurately describe the melting behavior of homogenous and periodic sequences. We collect melting data for several DNA oligos, and apply Monte Carlo simulations to establish force constants for the 10 dinucleotide steps (CG, CA, GC, AT, AG, AA, AC, TA, GG, TC). The experiments and numerical simulations confirm that the GG/CC dinucleotide stacking is remarkably unstable, compared with the stacking in GC/CG and CG/GC dinucleotide steps. The extended PBD model will facilitate thermodynamic and dynamic simulations of important genomic regions such as CpG islands and disease-related repeats. PMID:19264801
NASA Astrophysics Data System (ADS)
Blanc-Benon, Ph.; Berson, A.
2008-06-01
The development of high performance thermoacoustic refrigerators requires an efficient heat transport between the stack and the heat exchangers. A 1D nonlinear model for the thermal coupling of these two components is proposed in the case of a standing-wave thermaocoustic refrigerator. It shows the generation of temperature harmonics close to the edges of the plates that affects heat transport. In order to validate the model, the nonlinear temperature field close to the stack edges is measured using cold-wire anemometry.
A breathing wormlike chain model on DNA denaturation and bubble: effects of stacking interactions.
Kim, Jae-Yeol; Jeon, Jae-Hyung; Sung, Wokyung
2008-02-01
DNA stably exists as a double-stranded structure due to hydrogen-bonding and stacking interactions between bases. The stacking interactions are strengthened when DNA is paired, which results in great enhancement of bending rigidity. We study the effects of this stacking-induced stiffness difference on DNA denaturation and bubble formations. To this end, we model double-stranded DNA as a duplex of two semiflexible chains whose persistence length varies depending on the base-pair distance. Using this model, we perform the Langevin dynamics simulation to examine the characteristics of the denaturation transition and the statistics of the bubbles. We find that the inclusion of the stacking interactions causes the denaturation transition to be much sharper than otherwise. At physiological temperature, the stacking interactions prohibit the initiation of bubble formation but promote bubbles, once grown, to retain the large size. PMID:18266461
Nonlinear optical interactions in semiconductors
NASA Astrophysics Data System (ADS)
Salour, M. M.
1985-12-01
The optical pumping technique in GaAs has led to the development of a novel and highly sensitive optical temperature sensor. Completed is the experiment on two photon optical pumping in ZnO. An external cavity semiconductor laser involving ZnO as a gain medium was demonstrated under two-photon excitation. This laser should have a major impact on the development of tunable blue-green radiation for submarine communication. Completed is a paper on heat buildup in semiconductor platelets. New lasers are used to explore elementary excitation in optical thin film layers of semiconductors. This has led to the first demonstration of the feasibility of room temperature operation of a tunable coherent source involving multiple quantum well material. Completed is the construction of a simple remote (non-contact) temperature sensor to directly measure heat buildup in semiconductor materials as a result of high power optical laser excitation. Finally, an experiment involving optical frequency mixing to probe electrodynamics in the GaAlAs multiple quantumwell and superlattice structures, utilizing two recently constructed tunabel laser systems,has been successful. Attempts were focused on observing a number of new optical effects including nonlinear absorption and transmission phenomena, enhanced spontaneous and stimulated light scattering processes, etc. The construction of an external cavity semiconductor HgCdTe has been successful.
NASA Astrophysics Data System (ADS)
Suponitsky, Kyrill Yu; Masunov, Artëm E.
2013-09-01
Theoretical estimation of nonlinear optical (NLO) properties is an important step in systematic search for optoelectronic materials. Density functional theory methods are often used to predict first molecular hyperpolarizability for compounds in advance of their synthesis. However, design of molecular NLO materials require an estimation of the bulk properties, which are often approximated as additive superposition of molecular tensors. It is therefore important to evaluate the accuracy of this additive approximation and estimate the extent by which intermolecular interactions influence the first molecular hyperpolarizability β. Here we focused on the stacking aggregates, including up to 12 model molecules (pNA and ANS) and observed enhancement and suppression of molecular hyperpolarizability relative to the additive sum. We found that degree of nonadditivity depends on relative orientation of the molecular dipole moments and does not correlate with intermolecular interaction energy. Frenkel exciton model, based on dipole-dipole approximation can be used for qualitative prediction of intermolecular effects. We report on inaccuracy of this model for the molecules with long π-systems that are significantly shifted relative to each other, when dipole-dipole approximation becomes inaccurate. To obtain more detailed information on the effect of intermolecular interactions on β we proposed electrostatic approach which accounts for the mutual polarization of the molecules by each other. We measure the induced polarization of each molecule in the aggregate by the charge of its donor (or acceptor) group. The proposed approach demonstrates linear correlation βFF vs βelm (estimated by finite field theory and electrostatic model, respectively) and allows decomposition of the hyperpolarizability for a molecular aggregate into separate molecular contributions. We used this decomposition to analyze the reasons of deviation of aggregate β from additivity, as well as the
Relative substituent position on the strength of π-π stacking interactions
Emenike, Bright U.; Alverez, Celeste N.; Rakovan, John; Kirschbaum, Kristin; Jain, Nirbhay
2010-01-01
It was observed that the relative position of the arene substituents have a profound influence on the strength of π-π stacking in the 9-benzyl substituted triptycene system. A new series of model compounds (3a-i) capable of revealing quantitatively π-π stacking interactions was studied. This series of compounds (3a-i) has an ortho substituted methyl group in one of the two interacting arenes and the syn/anti ratios were determined and compared to a series previously studied compounds (4a-i) that have a para methyl group on the corresponding arene. A greater than 50% increase in the strength of π-π stacking interactions was observed with the methyl group in the ortho position comparing to that in the para position. No difference in π-π stacking interactions was observed when the other aromatic ring was a pentafluorobenzoate group. PMID:20209117
Stacking Interactions between 9-Methyladenine and Heterocycles Commonly Found in Pharmaceuticals.
An, Yi; Doney, Analise C; Andrade, Rodrigo B; Wheeler, Steven E
2016-05-23
Complexes of 9-methyladenine with 46 heterocycles commonly found in drugs were located using dispersion-corrected density functional theory, providing a representative set of 408 unique stacked dimers. The predicted binding enthalpies for each heterocycle span a broad range, highlighting the strong dependence of heterocycle stacking interactions on the relative orientation of the interacting rings. Overall, the presence of NH and carbonyl groups lead to the strongest stacking interactions with 9-methyadenine, and the strength of π-stacking interactions is sensitive to the distribution of heteroatoms within the ring as well as the specific tautomer considered. Although molecular dipole moments provide a sound predictor of the strengths and orientations of the 28 monocyclic heterocycles considered, dipole moments for the larger fused heterocycles show very little correlation with the predicted binding enthalpies. PMID:27074615
Nonlinear, inelastic fast reactor subassembly interaction analyses
Sutherland, W.H.; Bard, F.E.
1983-01-01
Liquid Metal Fast Breeder Reactor (LMFBR) core structural design is complicated by the trade-offs associated with keeping the subassemblies closely packed for the neutronic considerations and accommodating the volumetric changes associated with irradiation swelling. The environmental variation across the reactor core results in temperature and neutron flux gradients across the subassemblies which in turn cause the subassemblies to bow as well as dilate and grow volumetrically. These deformations in a tightly packed reactor core cause the subassemblies to interact and can potentially result in excessive withdrawal loads during the refueling operations. ABADAN, a general purpose, nonlinear, inelastic, multi-dimensional finite element structural analysis computer code, was developed for the express purpose of solving large nonlinear problems as typified by the above interaction problems. For the subassembly interaction problem ABADAN has been applied to the solution of an interacting radial row of Fast Flux Test Facility (FFTF) fuel assemblies.
Experimental and theoretical insights in the alkene-arene intramolecular π-stacking interaction.
Corne, Valeria; Sarotti, Ariel M; Ramirez de Arellano, Carmen; Spanevello, Rolando A; Suárez, Alejandra G
2016-01-01
Chiral acrylic esters derived from biomass were developed as models to have a better insight in the aryl-vinyl π-stacking interactions. Quantum chemical calculations, NMR studies and experimental evidences demonstrated the presence of equilibriums of at least four different conformations: π-stacked and face-to-edge, each of them in an s-cis/s-trans conformation. The results show that the stabilization produced by the π-π interaction makes the π-stacked conformation predominant in solution and this stabilization is slightly affected by the electron density of the aromatic counterpart. PMID:27559414
Experimental and theoretical insights in the alkene–arene intramolecular π-stacking interaction
Corne, Valeria; Sarotti, Ariel M; Ramirez de Arellano, Carmen; Spanevello, Rolando A
2016-01-01
Summary Chiral acrylic esters derived from biomass were developed as models to have a better insight in the aryl–vinyl π-stacking interactions. Quantum chemical calculations, NMR studies and experimental evidences demonstrated the presence of equilibriums of at least four different conformations: π-stacked and face-to-edge, each of them in an s-cis/s-trans conformation. The results show that the stabilization produced by the π–π interaction makes the π-stacked conformation predominant in solution and this stabilization is slightly affected by the electron density of the aromatic counterpart. PMID:27559414
A theoretical study of π-stacking interactions in C-substituted tetrazoles.
Farrokhzadeh, Abdolkarim; Modarresi-Alam, Ali Reza; Akher, Farideh Badichi; Ebrahimi, Ali
2016-06-01
The π-stacking effects of benzene ring (Ben) with 1H- and 2H-tetrazole derivatives (1H-TZ-X and 2H-TZ-X) substituted at C5 (where X is Cl, COH, NO, NO2, CN, NH2, OH, OCH3, SH and H) has been investigated by the quantum mechanical calculations at the M06-2X/6-311++G** level. The results indicate the 1H-TZ-X||Ben complexes (|| donates π-stacking interaction) are more stable than 2H-TZ-X||Ben while in unstacked forms, 1H-TZ-X is less stable than 2H-TZ-X. All substituents enhance the π-stacking interaction relative to the unsubstituted ones and enhancement is higher for the electron-withdrawing substituents (EWSs). Also, investigation of the local and direct effect of substituents in stacking interaction showed that all substituents regardless of whether are electron donating or electron withdrawing have an additive effect in π-stacking interaction. Excellent correlations were found between the binding energies of the complexes and combination of substituent constant terms. The results showed that the electrostatic interaction alone is not responsible for stacking stabilization but charge penetration is important. Furthermore, analysis of aromaticity, AIM, ESP and NPA were investigated to obtain aromaticity index, non-bonding interactions, chemical reactivity and polarity (dipole moment), respectively. PMID:27258189
Pi-stacked interactions in explosive crystals: buffers against external mechanical stimuli.
Zhang, Chaoyang; Wang, Xiaochuan; Huang, Hui
2008-07-01
The pi-stacked interactions in some explosive crystal packing are discussed. Taking a typical pi-stacked explosive 2,4,6-trinitrobenzene-1,3,5-triamine (TATB) as a sample and using molecular simulations, we investigated the nature of the pi-stacked interactions versus the external mechanical stimuli causing possible slide and compression of explosives. As a result, between the neighbor layers in the TATB unit cell, the electrostatic attraction decreases with a little decrease of vdW attraction when its top layer slides, whereas the vdW attraction increases with a decrease of electrostatic attraction when TATB crystal is compressed along its c axis. Meanwhile, we studied the correlation between the pi-stacked structures and the impact sensitivities of explosives by means of three representatives including TATB with typical planar pi-stacked structures, 2,2-dinitroethylene-1,1-diamine (Fox-7) with wavelike pi-stacked structures, and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) without pi-stacked structure. The results showed that pi-stacked structures, particularly planar layers, can effectively buffer against external mechanical stimuli. That is, pi-stacked structures can partly convert the mechanical energy acting on them into their intermolecular interaction energy, to avoid the increase of the molecular vibration resulting in the explosive decomposition, the formation of hot spots, and the final detonation. This is another reason for the low mechanical sensitivity of pi-stacked explosives besides their stable conjugated molecular structures. PMID:18529058
Nonlinear electromagnetic interactions in energetic materials
Wood, Mitchell Anthony; Dalvit, Diego Alejandro; Moore, David Steven
2016-01-12
We study the scattering of electromagnetic waves in anisotropic energetic materials. Nonlinear light-matter interactions in molecular crystals result in frequency-conversion and polarization changes. Applied electromagnetic fields of moderate intensity can induce these nonlinear effects without triggering chemical decomposition, offering a mechanism for the nonionizing identification of explosives. We use molecular-dynamics simulations to compute such two-dimensional THz spectra for planar slabs made of pentaerythritol tetranitrate and ammonium nitrate. Finally, we discuss third-harmonic generation and polarization-conversion processes in such materials. These observed far-field spectral features of the reflected or transmitted light may serve as an alternative tool for standoff explosive detection.
A Numerical Study of Nonlinear Wave Interactions
NASA Astrophysics Data System (ADS)
de Bakker, A.; Tissier, M.; Ruessink, G.
2014-12-01
Nonlinear triad interactions redistribute energy among a wave field, which transforms the shape of the incident short waves (f = 0.05 - 2 Hz) and generates energy at infragravity frequencies (f = 0.005-0.05 Hz). Recently, it has been suggested that infragravity energy may dissipate by energy transfers from infragravity frequencies to either the (former) short-wave spectral peak, or through infragravity-infragravity self-interactions that cause the infragravity waves to steepen and to eventually break. To investigate these infragravity dissipation mechanisms, we use the non-hydrostatic SWASH model. In this study, we first validate the model with the high-resolution GLOBEX laboratory data set and then explore the dependence of the energy transfers, with a focus on infragravity frequencies, on beach slope. Consistent with previous studies we find that SWASH is able to reproduce the transformation and corresponding nonlinear energy transfers of shoreward propagating waves to great detail. Bispectral analysis is used to study the coupling between wave frequencies; nonlinear energy transfers are then quantified using the Boussinesq coupling coefficient. To obtain more detailed insight we divide the nonlinear interactions in four categories based on triads including 1) infragravity frequencies only, 2) two infragravity frequencies and one short-wave frequency, 3) one infragravity frequency and two short-wave frequencies and 4) short-wave frequencies only. Preliminary results suggest that interactions are rather weak on gently beach slopes (1:80) and, in the innermost part of the surf zone, are dominated by infragravity-infragravity interactions. On steeper slopes (1:20), interactions are stronger, but entirely dominated by those involving short-wave frequencies only. The dependence of the transfers on offshore wave conditions and beach shape will be explored too. Funded by NWO.
Stacking interaction and its role in kynurenic acid binding to glutamate ionotropic receptors.
Zhuravlev, Alexander V; Zakharov, Gennady A; Shchegolev, Boris F; Savvateeva-Popova, Elena V
2012-05-01
Stacking interaction is known to play an important role in protein folding, enzyme-substrate and ligand-receptor complex formation. It has been shown to make a contribution into the aromatic antagonists binding with glutamate ionotropic receptors (iGluRs), in particular, the complex of NMDA receptor NR1 subunit with the kynurenic acid (KYNA) derivatives. The specificity of KYNA binding to the glutamate receptors subtypes might partially result from the differences in stacking interaction. We have calculated the optimal geometry and binding energy of KYNA dimers with the four types of aromatic amino acid residues in Rattus and Drosophila ionotropic iGluR subunits. All ab initio quantum chemical calculations were performed taking into account electron correlations at MP2 and MP4 perturbation theory levels. We have also investigated the potential energy surfaces (PES) of stacking and hydrogen bonds (HBs) within the receptor binding site and calculated the free energy of the ligand-receptor complex formation. The energy of stacking interaction depends both on the size of aromatic moieties and the electrostatic effects. The distribution of charges was shown to determine the geometry of polar aromatic ring dimers. Presumably, stacking interaction is important at the first stage of ligand binding when HBs are weak. The freedom of ligand movements and rotation within receptor site provides the precise tuning of the HBs pattern, while the incorrect stacking binding prohibits the ligand-receptor complex formation. PMID:21833825
Quantifying the π-Stacking Interactions in Nitroarene Binding Sites of Proteins.
An, Yi; Bloom, Jacob W G; Wheeler, Steven E
2015-11-12
Stacking interactions in nitroarene binding sites of proteins were studied through analyses of structures in the protein data bank (PDB), as well as DFT and ab initio computations applied to model systems. Stacked dimers of mono-, di-, and trinitrobenzene with the amino acid side chains histidine (His), phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp) were optimized at the B97-D/TZV(2d,2p) level of theory. Binding energies for the global minimum dimer geometries were further refined at the estimated CCSD(T)/aug-cc-pVTZ level of theory. The results show that the interactions between aromatic amino acids and nitroarenes are very strong (up to -14.6 kcal mol(-1)), and the regiochemistry of the nitro substituents plays a significant role in the relative monomer orientations and strength of the interaction. In contrast to model stacked benzene dimers, effects of nitro substituents in stacking complexes with aromatic amino acid side chains are not perfectly additive. This is attributed to direct interactions of the nitro substituents with functional groups in the amino acid side chain. Overall, the strength of stacking interactions with these nitrobenzenes follows the order Trp > Tyr > Phe ≈ His. We also analyzed nitroarene binding sites in the PDB. Out of 216 selected crystal structures containing nitroarene ligands, 191 have nearby aromatic residues, providing 65 examples of π-stacking interactions involving a nitroarene. Of these, the representations of the different aromatic amino acids (Trp > Tyr > Phe > His) are correlated with the strength of model complexes of nitroarenes, with the exception of His. B97-D computations applied to complexes extracted from these crystal structures reveal that π-stacking interactions between the nitroarene and aromatic amino acid side chains exhibit a broad range of strengths, with many contributing significantly to binding. PMID:26491883
Nonlinear quantum optics mediated by Rydberg interactions
NASA Astrophysics Data System (ADS)
Firstenberg, O.; Adams, C. S.; Hofferberth, S.
2016-08-01
By mapping the strong interaction between Rydberg excitations in ultra-cold atomic ensembles onto single photons via electromagnetically induced transparency, it is now possible to realize a medium which exhibits a strong optical nonlinearity at the level of individual photons. We review the theoretical concepts and the experimental state-of-the-art of this exciting new field, and discuss first applications in the field of all-optical quantum information processing.
Beam-Plasma Interaction and Nonlinear Effects
Yoon, Peter H.
2009-11-10
This paper presents a survey of perturbative nonlinear plasma theory known as the weak turbulence theory. After the basic concepts and methodology of the weak turbulence theory are outlined in sufficient detail, numerical solutions of the weak turbulence theory obtained in the context of the beam-plasma interaction are compared against particle-in-cell (PIC) numerical simulations. It is demonstrated that theory and PIC simulation are in excellent agreement.
Kataev, Evgeny A; Shumilova, Tatiana A; Fiedler, Benjamin; Anacker, Tony; Friedrich, Joachim
2016-08-01
Stacking interactions between aromatic compounds and nucleobases are crucial in recognition of nucleotides and nucleic acids, but a comprehensive understanding of the strength and selectivity of these interactions in aqueous solution has been elusive. To this end, model complexes have been designed and analyzed by experiment and theory. For the first time, stacking free energies between five nucleobases and anthracene were determined experimentally from thermodynamic double mutant cycles. Three different experimental methods were proposed and evaluated. The dye prefers to bind nucleobases in the order (kcal/mol): G (1.3) > T (0.9) > U (0.8) > C (0.5) > A (0.3). The respective trend of interaction free energies extracted from DFT calculations correlates to that obtained experimentally. Analysis of the data suggests that stacking interactions dominate over hydrophobic effects in an aqueous solution and can be predicted with DFT calculations. PMID:27314892
Dynamic investigation of PEFC stacks in interaction with the air supply system
NASA Astrophysics Data System (ADS)
Philipps, F.; Simons, G.; Schiefer, K.
This paper explores the behaviour of a dynamically operated fuel cell system regarding to an automotive application, examining the air supply and their interaction with the fuel cell stacks. The dynamic limits of stack operation are also discussed. Finally, the paper provides a description of the test facility used in these investigations. The research of dynamically operated fuel cell stacks shows that in order to achieve high energy efficiency, a power-dependent modulation of the pressure and flow rate of the air supply is necessary. A test facility designed for energy management and power train research (up to 42 kW) was used for the experiment. A number of 11.5 kW fuel cell stacks was examined experimentally with respect to performance in interaction with the air supply in stationary and dynamic operation. The stacks were tested individually and in parallel. All of them were operated "dead-end" on the hydrogen side. Experimental results varying the parameters and load curves applied to the air supply system are given in the paper. The results show different dynamic behaviours between the stacks and a substantial difference in efficiency and dynamic response of the fuel cell system operated with different strategies. The results of different operating strategies for fuel cell systems, with respect to the interaction between the fuel cell stack and the air supply and in their dependency on air mass flow and pressure level are presented. The examinations were done with the test facility using real current demand profile of the experimental car HyLite ® from zero to full load and the New European Drive Cycle (NEDC).
Sredojević, Dušan N; Petrović, Predrag V; Janjić, Goran V; Brothers, Edward N; Hall, Michael B; Zarić, Snežana D
2016-01-01
The strength of the stacking interactions in the bipy complexes of nickel, palladium, and platinum, [M(CN)2 bipy]2 (M = Ni, Pd, Pt), was calculated using the ωB97xD/def2-TZVP method. The results show that for all considered geometries, interactions are the strongest for platinum, and weakest for nickel complexes, as a result of higher dispersion contributions of platinum over the palladium and nickel complexes. It was also shown that strength of interactions considerably rises with an increase of the stacking overlap area. As a consequence of the favorable electrostatic term, the strength of interactions also rises when metal atom and cyano ligands are involved in the overlap with bipy ligand. The strongest interaction was calculated in the platinum complex, for the geometry that has overlap of metal and cyano ligands with bipy ligand with an energy of -39.80 kcal mol(-1). The energies for similar geometries of palladium and nickel complexes are -34.60 and -32.45 kcal mol(-1). These energies, remarkably, exceed the strength of the stacking interactions between organic aromatic molecules. These results can be of importance in all systems with stacking interactions, from materials to biomolecules. PMID:26757913
Double pancake bonds: pushing the limits of strong π-π stacking interactions.
Cui, Zhong-hua; Lischka, Hans; Beneberu, Habtamu Z; Kertesz, Miklos
2014-09-17
The concept of a double-bonded pancake bonding mechanism is introduced to explain the extremely short π-π stacking contacts in dimers of dithiatriazines. While ordinary single pancake bonds occur between radicals and already display significantly shorter interatomic distances in comparison to van der Waals (vdW) contacts, the double-bonded pancake dimer is based on diradicaloid or antiaromatic molecules and exhibits even shorter and stronger intermolecular bonds that breach into the range of extremely stretched single bonds in terms of bond distances and binding energies. These properties give rise to promising possibilities in the design of new materials with high electrical conductivity and for the field of spintronics. The analysis of the double pancake bond is based on cutting edge electron correlation theory combining multireference (nondynamical) effects and dispersion (dynamical) contributions in a balanced way providing accurate interaction energies and distributions of unpaired spins. It is also shown that the present examples do not stand isolated but that similar mechanisms operate in several analogous nonradical molecular systems to form double-bonded π-stacking pancake dimers. We report on the amazing properties of a new type of stacking interaction mechanism between π conjugated molecules in the form of a "double pancake bond" which breaks the record for short intermolecular distances and provides formidable strength for some π-π stacking interactions. PMID:25203200
Stacking of purines in water: the role of dipolar interactions in caffeine.
Tavagnacco, L; Di Fonzo, S; D'Amico, F; Masciovecchio, C; Brady, J W; Cesàro, A
2016-05-11
During the last few decades it has been ascertained that base stacking is one of the major contributions stabilizing nucleic acid conformations. However, the understanding of the nature of the interactions involved in the stacking process remains under debate and it is a subject of theoretical and experimental studies. Structural similarity between purine bases (guanine and adenine) in DNA and the caffeine molecule makes caffeine an excellent model for the purine bases. The present study clearly shows that dipolar interactions play a fundamental role in determining stacking of purine molecules in solution. In order to reach this achievement, polarized ultraviolet Raman resonant scattering experiments have been carried out on caffeine aqueous solutions as a function of concentration and temperature. The investigation pointed out at the aggregation and solvation properties, particularly at elevated temperatures. Kubo-Anderson theory was used as a framework to investigate the non-coincidence effect (NCE) occurring in the totally symmetric breathing modes of the purine rings, and in the bending modes of the methyl groups of caffeine. The NCE concentration dependence shows that caffeine aggregation at 80 °C occurs by planar stacking of the hydrophobic faces. The data clearly indicate that dipolar interactions determine the reorientational motion of the molecules in solution and are the driving force for the stacking of caffeine. In parallel, the observed dephasing times imply a change in caffeine interactions as a function of temperature and concentration. A decrease, at low water content, of the dephasing time for the ring breathing vibration mode indicates that self-association alters the solvation structure that is detectable at low concentration. These results are in agreement with simulation predictions and serve as an important validation of the models used in those calculations. PMID:27127808
Dynamics of dislocation interactions with stacking-fault tetrahedra at high temperature
NASA Astrophysics Data System (ADS)
Briceño, M.; Kacher, J.; Robertson, I. M.
2013-02-01
The interaction process between dislocations and large stacking-fault tetrahedra was observed in real time at high temperature during deformation experiments in situ in the transmission electron microscope. Dislocation interactions with tetrahedra resulted in them being annihilated and converted to another defect type. Dislocation bypass of the tetrahedra occurred by cross-slip. The latter interaction occurred slowly and halted the progress of the dislocation. Annihilation versus bypass by dislocation cross-slip was dictated by the location at which the slip plane intersected the tetrahedron - on the face or along the edges with the stair-rod dislocations. In general, the interactions, at best, were weakly temperature dependent.
The influence of arene-ring size on stacking interaction with canonical base pairs
NASA Astrophysics Data System (ADS)
Formánek, Martin; Burda, Jaroslav V.
2014-04-01
Stacking interactions between aromatic molecules (benzene, p-cymene, biphenyl, and di- and tetra-hydrogen anthracene) and G.C and A.T canonical Watson-Crick (WC) base pairs are explored. Two functionals with dispersion corrections: ω-B97XD and B3LYP-D3 are used. For a comparison also the MP2 and B3LYP-D3/PCM methods were used for the most stable p-cymene…WC geometries. It was found that the stacking interaction increases with the size of π-conjugation system. Its extent is in agreement with experimental finding on anticancer activity of Ru(II) piano-stool complexes where intercalation of these aromatic molecules should play an important role. The explored structures are considered as ternary system so that decomposition of the interaction energy to pairwise and non-additivity contributions is also examined.
Cooper, Valentino R; Thonhauser, T; Langreth, David C
2008-05-28
We apply the van der Waals density functional (vdW-DF) to study hydrogen bonding and stacking interactions between nucleobases. The excellent agreement of our results with high level quantum chemical calculations highlights the value of the vdW-DF for first-principles investigations of biologically important molecules. Our results suggest that, in the case of hydrogen-bonded nucleobase pairs, dispersion interactions reduce the cost of propeller twists while having a negligible effect on buckling. Furthermore, the efficient scaling of DFT methods allowed for the easy optimization of separation distance between nucleobase stacks, indicating enhancements in the interaction energy of up to 3 kcalmol over previous fixed distance calculations. We anticipate that these results are significant for extending the vdW-DF method to model larger vdW complexes and biological molecules. PMID:18513005
NASA Astrophysics Data System (ADS)
Wendt, P. D.; Coyle, E. J.; Gallagher, N. C., Jr.
1986-08-01
A large class of easily implemented nonlinear filters called stack filters are discussed which includes the rank order operators in addition to the compositions of morphological operators. Techniques similar to those used to determine the root signal behavior of median filters are employed to study the convergence properties of the filters, and necessary conditions for a stack filter to preserve monotone regions or edges in signals, and the output distribution of the filters, are obtained. Among the stack filters of window width three are found asymmetric median filters in which one removes only positive going edges, the other removes only negative going edges, while the median filter removes impulses of both signs.
Nonlinear inversion of pre-stack seismic data using variable metric method
NASA Astrophysics Data System (ADS)
Zhang, Fanchang; Dai, Ronghuo
2016-06-01
At present, the routine method to perform AVA (Amplitude Variation with incident Angle) inversion is based on the assumption that the ratio of S-wave velocity to P-wave velocity γ is a constant. However, this simplified assumption does not always hold, and it is necessary to use nonlinear inversion method to solve it. Based on Bayesian theory, the objective function for nonlinear AVA inversion is established and γ is considered as an unknown model parameter. Then, variable metric method with a strategy of periodically variational starting point is used to solve the nonlinear AVA inverse problem. The proposed method can keep the inverted reservoir parameters approach to the actual solution and has been performed on both synthetic and real data. The inversion results suggest that the proposed method can solve the nonlinear inverse problem and get accurate solutions even without the knowledge of γ.
Stack zooming for multifocus interaction in skewed-aspect visual spaces.
Javed, Waqas; Elmqvist, Niklas
2013-08-01
Many 2D visual spaces have a virtually one-dimensional nature with very high aspect ratio between the dimensions: examples include time-series data, multimedia data such as sound or video, text documents, and bipartite graphs. Common among these is that the space can become very large, e.g., temperature measurements could span a long time period, surveillance video could cover entire days or weeks, and documents can have thousands of pages. Many analysis tasks for such spaces require several foci while retaining context and distance awareness. In this extended version of our IEEE PacificVis 2010 paper, we introduce a method for supporting this kind of multifocus interaction that we call stack zooming. The approach is based on building hierarchies of 1D strips stacked on top of each other, where each subsequent stack represents a higher zoom level, and sibling strips represent branches in the exploration. Correlation graphics show the relation between stacks and strips of different levels, providing context and distance awareness for the foci. The zoom hierarchies can also be used as graphical histories and for communicating insights to stakeholders and can be further extended with annotation and integrated statistics. PMID:23744266
Chen, L.X.; Laible, P.D.; Spano, F.C.; Manas, E.S.
1997-09-01
Enhancement of the nonresonant second order molecular hyperpolarizabilities {gamma} were observed in stacked macrocyclic molecular systems, previously in a {micro}-oxo silicon phthalocyanine (SiPcO) monomer, dimer and trimer series, and now in bacteriochlorophyll a (BChla) arrays of light harvesting (LH) proteins. Compared to monomeric BChla in a tetrahydrofuran (THF) solution, the <{gamma}> for each macrocycle was enhanced in naturally occurring stacked macrocyclic molecular systems in the bacterial photosynthetic LH proteins where BChla`s are arranged in tilted face-to-face arrays. In addition, the {gamma} enhancement is more significant in B875 of LH1 than in B850 in LH2. Theoretical modeling of the nonresonant {gamma} enhancement using simplified molecular orbitals for model SiPcO indicated that the energy level of the two photon state is crucial to the {gamma} enhancement when a two photon process is involved, whereas the charge transfer between the monomers is largely responsible when one photon near resonant process is involved. The calculated results can be extended to {gamma} enhancement in B875 and B850 arrays, suggesting that BChla in B875 are more strongly coupled than in B850. In addition, a 50--160 fold increase in <{gamma}> for the S{sub 1} excited state of relative to S{sub 0} of bacteriochlorophyll in vivo was observed which provides an alternative method for probing excited state dynamics and a potential application for molecular switching.
Folic acid-polydopamine nanofibers show enhanced ordered-stacking via π-π interactions.
Fan, Hailong; Yu, Xiang; Liu, Yang; Shi, Zujin; Liu, Huihui; Nie, Zongxiu; Wu, Decheng; Jin, Zhaoxia
2015-06-21
Recent research has indicated that polydopamine and synthetic eumelanins are optoelectronic biomaterials in which one-dimensional aggregates composed of ordered-stacking oligomers have been proposed as unique organic semiconductors. However, improving the ordered-stacking of oligomers in polydopamine nanostructures is a big challenge. Herein, we first demonstrate how folic acid molecules influence the morphology and nanostructure of polydopamine via tuning the π-π interactions of oligomers. MALDI-TOF mass spectrometry reveals that porphyrin-like tetramers are characteristic of folic acid-polydopamine (FA-PDA) nanofibers. X-ray diffraction combined with simulation studies indicate that these oligomers favour aggregation into graphite-like ordered nanostructures via strong π-π interactions. High-resolution TEM characterization of carbonized FA-PDA hybrids show that in FA-PDA nanofibers the size of the graphite-like domains is over 100 nm. The addition of folic acid in polydopamine enhances the ordered stacking of oligomers in its nanostructure. Our study steps forward to discover the mystery of the structure-property relationship of FA-PDA hybrids. It paves a way to optimize the properties of PDA through the design and selection of oligomer structures. PMID:25959650
Cy3-DNA Stacking Interactions Strongly Depend on the Identity of the Terminal Basepair
Spiriti, Justin; Binder, Jennifer K.; Levitus, Marcia; van der Vaart, Arjan
2011-01-01
We characterized the effect of the first basepair on the conformational dynamics of the fluorescent dye Cy3 attached to the 5′ end of double-stranded DNA using Gaussian-mixture adaptive umbrella sampling simulations. In the simulations, the sampling of all five dihedral angles along the linker was enhanced, so that both stacked and unstacked states were sampled. The affinity of Cy3 for a T·A basepair (with the dye attached to T) was found to be significantly less than for the other basepairs. This was verified experimentally by measuring the activation energies for cis-trans isomerization of the dye. The simulation and experimental results indicate the existence of partially unstacked conformations amenable to photoisomerization. The simulations also showed that stacking of Cy3 straightens the DNA while stabilizing the first basepair. Our findings indicate that fluorescence is modulated by Cy3-DNA interactions in a sequence-dependent manner. PMID:21320450
NASA Astrophysics Data System (ADS)
Meiler, M.; Andre, D.; Schmid, O.; Hofer, E. P.
Intelligent energy management is a cost-effective key path to realize efficient automotive drive trains [R. O'Hayre, S.W. Cha, W. Colella, F.B. Prinz. Fuel Cell Fundamentals, John Wiley & Sons, Hoboken, 2006]. To develop operating strategy in fuel cell drive trains, precise and computational efficient models of all system components, especially the fuel cell stack, are needed. Should these models further be used in diagnostic or control applications, then some major requirements must be fulfilled. First, the model must predict the mean fuel cell voltage very precisely in all possible operating conditions, even during transients. The model output should be as smooth as possible to support best efficient optimization strategies of the complete system. At least, the model must be computational efficient. For most applications, a difference between real fuel cell voltage and model output of less than 10 mV and 1000 calculations per second will be sufficient. In general, empirical models based on system identification offer a better accuracy and consume less calculation resources than detailed models derived from theoretical considerations [J. Larminie, A. Dicks. Fuel Cell Systems Explained, John Wiley & Sons, West Sussex, 2003]. In this contribution, the dynamic behaviour of the mean cell voltage of a polymer-electrolyte-membrane fuel cell (PEMFC) stack due to variations in humidity of cell's reactant gases is investigated. The validity of the overall model structure, a so-called general Hammerstein model (or Uryson model), was introduced recently in [M. Meiler, O. Schmid, M. Schudy, E.P. Hofer. Dynamic fuel cell stack model for real-time simulation based on system identification, J. Power Sources 176 (2007) 523-528]. Fuel cell mean voltage is calculated as the sum of a stationary and a dynamic voltage component. The stationary component of cell voltage is represented by a lookup-table and the dynamic voltage by a parallel placed, nonlinear transfer function. A
NASA Astrophysics Data System (ADS)
Tamura, Ryo; Tanaka, Shu
2013-11-01
We study the phase transition behavior of a frustrated Heisenberg model on a stacked triangular lattice by Monte Carlo simulations. The model has three types of interactions: the ferromagnetic nearest-neighbor interaction J1 and antiferromagnetic third nearest-neighbor interaction J3 in each triangular layer and the ferromagnetic interlayer interaction J⊥. Frustration comes from the intralayer interactions J1 and J3. We focus on the case that the order parameter space is SO(3)×C3. We find that the model exhibits a first-order phase transition with breaking of the SO(3) and C3 symmetries at finite temperature. We also discover that the transition temperature increases but the latent heat decreases as J⊥/J1 increases, which is opposite to the behavior observed in typical unfrustrated three-dimensional systems.
Conditional nonlinear operations by sequential Jaynes-Cummings interactions
NASA Astrophysics Data System (ADS)
Park, Kimin; Marek, Petr; Filip, Radim
2016-07-01
Nonlinear operations are essential for quantum information processing. We propose a way of implementing a class of nonlinear operations by sequential application of conditional gates based on Jaynes-Cummings (JC) interaction and projective measurements. The scheme has many advantages over the previously proposed all-optical methods and can be applied in several available experimental platforms, such as cavity quantum electrodynamics, trapped ions, and others. We demonstrate performance of the approach on the example of the cubic nonlinearity. We show several different ways in which the full nonlinear operation can be decomposed into sequences of the individual gates, and we compare their performance.
Non-linear interaction of elastic waves in rocks
NASA Astrophysics Data System (ADS)
Kuvshinov, B. N.; Smit, T. J. H.; Campman, X. H.
2013-09-01
We study theoretically the interaction of elastic waves caused by non-linearities of rock elastic moduli, and assess the possibility to use this phenomenon in hydrocarbon exploration and in the analysis of rock samples. In our calculations we use the five-constant model by Gol'dberg. It is shown that the interaction of plane waves in isotropic solids is completely described by five coupling coefficients, which have the same order of magnitude. By considering scattering of compressional waves generated by controlled sources at the Earth surface from a non-linear layer at the subsurface, we conclude that non-linear signals from deep formations are unlikely to be measured with the current level of technology. Our analysis of field tests where non-linear signals were measured, suggests that these signals are generated either in the shallow subsurface or in the vicinity of sources. Non-linear wave interaction might be observable in lab tests with focused ultrasonic beams. In this case, the non-linear response is generated in the secondary parametric array formed by linear beams scattered from inclusions. Although the strength of this response is controlled by non-linearity of the surrounding medium rather than by non-linearity of inclusions, its measurement can help to obtain better images of rock samples.
He, Linna; Yang, Zhihao; Zhao, Zhehuan; Lin, Hongfei; Li, Yanpeng
2013-01-01
Drug-drug interaction (DDI) detection is particularly important for patient safety. However, the amount of biomedical literature regarding drug interactions is increasing rapidly. Therefore, there is a need to develop an effective approach for the automatic extraction of DDI information from the biomedical literature. In this paper, we present a Stacked Generalization-based approach for automatic DDI extraction. The approach combines the feature-based, graph and tree kernels and, therefore, reduces the risk of missing important features. In addition, it introduces some domain knowledge based features (the keyword, semantic type, and DrugBank features) into the feature-based kernel, which contribute to the performance improvement. More specifically, the approach applies Stacked generalization to automatically learn the weights from the training data and assign them to three individual kernels to achieve a much better performance than each individual kernel. The experimental results show that our approach can achieve a better performance of 69.24% in F-score compared with other systems in the DDI Extraction 2011 challenge task. PMID:23785452
Dislocation-stacking fault tetrahedron interaction: what can we learn from atomic scale modelling.
Osetskiy, Yury N; Stoller, Roger E; Matsukawa, Yoshitaka
2004-01-01
The high number density of stacking fault tetrahedra (SFTs) observed in irradiated fcc metals suggests that they should contribute to radiation-induced hardening and, therefore, taken into account when estimating mechanical properties changes of irradiated materials. The central issue is describing the individual interaction between a moving dislocation and an SFT, which is characterized by a very fine size scale, {approx}100 nm. This scale is amenable to both in situ TEM experiments and large-scale atomic modelling. In this paper we present results of an atomistic simulation of dislocation-SFT interactions using molecular dynamics (MD). The results are compared with observations from in situ deformation experiments. It is demonstrated that in some cases the simulations and experimental observations are quite similar, suggesting a reasonable interpretation of experimental observations.
Ghost Dark Energy with Non-Linear Interaction Term
NASA Astrophysics Data System (ADS)
Ebrahimi, E.
2016-06-01
Here we investigate ghost dark energy (GDE) in the presence of a non-linear interaction term between dark matter and dark energy. To this end we take into account a general form for the interaction term. Then we discuss about different features of three choices of the non-linear interacting GDE. In all cases we obtain equation of state parameter, w D = p/ ρ, the deceleration parameter and evolution equation of the dark energy density parameter (Ω D ). We find that in one case, w D cross the phantom line ( w D < -1). However in two other classes w D can not cross the phantom divide. The coincidence problem can be solved in these models completely and there exist good agreement between the models and observational values of w D , q. We study squared sound speed {vs2}, and find that for one case of non-linear interaction term {vs2} can achieves positive values at late time of evolution.
Nonlinear interaction of meta-atoms through optical coupling
Slobozhanyuk, A. P.; Kapitanova, P. V.; Filonov, D. S.; Belov, P. A.; Powell, D. A.; Shadrivov, I. V.; Kivshar, Yu. S.; Lapine, M.; McPhedran, R. C.
2014-01-06
We propose and experimentally demonstrate a multi-frequency nonlinear coupling mechanism between split-ring resonators. We engineer the coupling between two microwave resonators through optical interaction, whilst suppressing the direct electromagnetic coupling. This allows for a power-dependent interaction between the otherwise independent resonators, opening interesting opportunities to address applications in signal processing, filtering, directional coupling, and electromagnetic compatibility.
Zhang, Tian-biao; Zhang, Chang-lin; Dong, Zai-li; Guan, Yi-fu
2015-01-01
As one of the most crucial properties of DNA, the structural stability and the mechanical strength are attracting a great attention. Here, we take advantage of high force resolution and high special resolution of Atom Force Microscope and investigate the mechanical force of DNA duplexes. To evaluate the base pair hydrogen bond strength and base stacking force in DNA strands, we designed two modes (unzipping and stretching) for the measurement rupture forces. Employing k-means clustering algorithm, the ruptured force are clustered and the mean values are estimated. We assessed the influence of experimental parameters and performed the force evaluation for DNA duplexes of pure dG/dC and dA/dT base pairs. The base binding strength of single dG/dC and single dA/dT were estimated to be 20.0 ± 0.2 pN and 14.0 ± 0.3 pN, respectively, and the base stacking interaction was estimated to be 2.0 ± 0.1 pN. Our results provide valuable information about the quantitative evaluation of the mechanical properties of the DNA duplexes. PMID:25772017
Enhanced energy transport owing to nonlinear interface interaction
Su, Ruixia; Yuan, Zongqiang; Wang, Jun; Zheng, Zhigang
2016-01-01
It is generally expected that the interface coupling leads to the suppression of thermal transport through coupled nanostructures due to the additional interface phonon-phonon scattering. However, recent experiments demonstrated that the interface van der Waals interactions can significantly enhance the thermal transfer of bonding boron nanoribbons compared to a single freestanding nanoribbon. To obtain a more in-depth understanding on the important role of the nonlinear interface coupling in the heat transports, in the present paper, we explore the effect of nonlinearity in the interface interaction on the phonon transport by studying the coupled one-dimensional (1D) Frenkel-Kontorova lattices. It is found that the thermal conductivity increases with increasing interface nonlinear intensity for weak inter-chain nonlinearity. By developing the effective phonon theory of coupled systems, we calculate the dependence of heat conductivity on interfacial nonlinearity in weak inter-chain couplings regime which is qualitatively in good agreement with the result obtained from molecular dynamics simulations. Moreover, we demonstrate that, with increasing interface nonlinear intensity, the system dimensionless nonlinearity strength is reduced, which in turn gives rise to the enhancement of thermal conductivity. Our results pave the way for manipulating the energy transport through coupled nanostructures for future emerging applications. PMID:26787363
Enhanced energy transport owing to nonlinear interface interaction.
Su, Ruixia; Yuan, Zongqiang; Wang, Jun; Zheng, Zhigang
2016-01-01
It is generally expected that the interface coupling leads to the suppression of thermal transport through coupled nanostructures due to the additional interface phonon-phonon scattering. However, recent experiments demonstrated that the interface van der Waals interactions can significantly enhance the thermal transfer of bonding boron nanoribbons compared to a single freestanding nanoribbon. To obtain a more in-depth understanding on the important role of the nonlinear interface coupling in the heat transports, in the present paper, we explore the effect of nonlinearity in the interface interaction on the phonon transport by studying the coupled one-dimensional (1D) Frenkel-Kontorova lattices. It is found that the thermal conductivity increases with increasing interface nonlinear intensity for weak inter-chain nonlinearity. By developing the effective phonon theory of coupled systems, we calculate the dependence of heat conductivity on interfacial nonlinearity in weak inter-chain couplings regime which is qualitatively in good agreement with the result obtained from molecular dynamics simulations. Moreover, we demonstrate that, with increasing interface nonlinear intensity, the system dimensionless nonlinearity strength is reduced, which in turn gives rise to the enhancement of thermal conductivity. Our results pave the way for manipulating the energy transport through coupled nanostructures for future emerging applications. PMID:26787363
Collective Political Opinion Formation in Nonlinear Social Interaction
NASA Astrophysics Data System (ADS)
Kim, Soo Yong; Park, Chung Hyun; Kim, Kyungsik
We have presented a numerical model of a collective opinion formation procedure to explain political phenomena such as two-party and multi-party systems in politics, political unrest, military coup d'etats and netizen revolutions. Nonlinear interaction with binary and independent decision making processes can yield various collective behaviors or collective political opinions. Statistical physics and nonlinear dynamics may provide useful tools to study various socio-political dynamics.
Influence of the π–π interaction on the hydrogen bonding capacity of stacked DNA/RNA bases
Mignon, Pierre; Loverix, Stefan; Steyaert, Jan; Geerlings, Paul
2005-01-01
The interplay between aromatic stacking and hydrogen bonding in nucleobases has been investigated via high-level quantum chemical calculations. The experimentally observed stacking arrangement between consecutive bases in DNA and RNA/DNA double helices is shown to enhance their hydrogen bonding ability as opposed to gas phase optimized complexes. This phenomenon results from more repulsive electrostatic interactions as is demonstrated in a model system of cytosine stacked offset-parallel with substituted benzenes. Therefore, the H-bonding capacity of the N3 and O2 atoms of cytosine increases linearly with the electrostatic repulsion between the stacked rings. The local hardness, a density functional theory-based reactivity descriptor, appears to be a key index associated with the molecular electrostatic potential (MEP) minima around H-bond accepting atoms, and is inversely proportional to the electrostatic interaction between stacked molecules. Finally, the MEP minima on surfaces around the bases in experimental structures of DNA and RNA–DNA double helices show that their hydrogen bonding capacity increases when taking more neighboring (intra-strand) stacking partners into account. PMID:15788750
Zhang, Kenan; Hu, Shuhong; Zhang, Yun; Zhang, Tianning; Zhou, Xiaohao; Sun, Yan; Li, Tian-Xin; Fan, Hong Jin; Shen, Guozhen; Chen, Xin; Dai, Ning
2015-03-24
Strain engineering is an effective method to tune the properties of electrons and phonons in semiconductor materials, including two-dimensional (2D) layered materials (e.g., MoS2 or graphene). External artificial stress (ExAS) or heterostructure stacking is generally required to induce strains for modulating semiconductor bandgaps and optoelectronic functions. For layered materials, the van der Waals-stacked interlayer interaction (vdW-SI) has been considered to dominate the interlayer stacking and intralayer bonding. Here, we demonstrate self-induced uniaxial strain in the MoS2 monolayer without the assistance of ExAS or heterostructure stacking processes. The uniaxial strain occurring in local monolayer regions is manifested by the Raman split of the in-plane vibration modes E2g(1) and is essentially caused by local vdW-SI within the single layer MoS2 due to a unique symmetric bilayer stacking. The local stacked configuration and the self-induced uniaxial strain may provide improved understanding of the fundamental interlayer interactions and alternative routes for strain engineering of layered structures. PMID:25716291
Nonlinear Optical Interactions in Plasmas at JILA
NASA Astrophysics Data System (ADS)
Dollar, F.; Hickstein, D. D.; Popmintchev, D.; Becker, A.; Ellis, J.; Hernandez-Garcia, C.; Jaron-Becker, A.; Popmintchev, T.; Xiong, W.; Murnane, M. M.; Kapteyn, H. C.; Dukovic, G.; Jimenez, J.; Palm, B.; Schnitzenbaumer, K.; Perez-Hernandez, J.; Gaeta, A.; Gao, X.; Shim, B.; Plaja, L.; Levis, R.; Tarazkar, M.; Foord, M. E.; Gaffney, J. A.; Libby, S. B.
2014-10-01
We present data from two recent experiments. First, we demonstrate direct observations of localized light absorption in a single nanoparticle irradiated by a strong femtosecond laser field. By imaging the photoion momentum distribution resulting from plasma formation in a laser-irradiated nanostructure, we map the spatial location of the highly localized plasma and thereby image the nanoscale light absorption. Secondly, we show the high linear and nonlinear UV refractive indices of both neutral atoms and ions compensate for plasma dispersion, even in multiply-ionized gases. The experimental work was primarily funded by DOE Grant Number: DE-SC0008803, the DARPA PULSE program, and ARO W911NF-12-1-0436.
Atomic-Scale Study of Dislocation-Stacking Fault Tetrahedron Interactions. Part I: Mechanisms.
Osetskiy, Yury N; Rodney, David; Bacon, David J
2006-01-01
Stacking fault tetrahedra (SFTs) are formed under irradiation in fcc metals and alloys. The high number density of SFTs observed suggests that they should contribute to radiation-induced hardening and, therefore, be taken into account when estimating mechanical property changes of irradiated materials. The key issue in this is to describe the interaction between a moving dislocation and an individual SFT, which is distinguished by a small physical size of the order of {approx}1-10 nm. We have performed atomistic simulations of edge and screw dislocations interacting with SFTs of different sizes at different temperatures and strain rates. Five possible interaction outcomes have been identified, involving either partial absorption, or shearing or restoration of SFTs. The mechanisms that give rise to these processes are described and their dependence on interaction parameters, such as SFT size, dislocation-SFT geometry, temperature and stress/strain rate are determined. Mechanisms that help to explain the formation of defect-free channels cleared by gliding dislocations, as observed experimentally, are also discussed. Hardening due to the various mechanisms and their dependence on loading conditions will be presented in a following paper (Part II).
Enhanced nonlinear interactions in quantum optomechanics via mechanical amplification
NASA Astrophysics Data System (ADS)
Lemonde, Marc-Antoine; Didier, Nicolas; Clerk, Aashish A.
2016-04-01
The quantum nonlinear regime of optomechanics is reached when nonlinear effects of the radiation pressure interaction are observed at the single-photon level. This requires couplings larger than the mechanical frequency and cavity-damping rate, and is difficult to achieve experimentally. Here we show how to exponentially enhance the single-photon optomechanical coupling strength using only additional linear resources. Our method is based on using a large-amplitude, strongly detuned mechanical parametric drive to amplify mechanical zero-point fluctuations and hence enhance the radiation pressure interaction. It has the further benefit of allowing time-dependent control, enabling pulsed schemes. For a two-cavity optomechanical set-up, we show that our scheme generates photon blockade for experimentally accessible parameters, and even makes the production of photonic states with negative Wigner functions possible. We discuss how our method is an example of a more general strategy for enhancing boson-mediated two-particle interactions and nonlinearities.
New nucleotide pairs for stable DNA triplexes stabilized by stacking interaction.
Mizuta, Masahiro; Banba, Jun-ichi; Kanamori, Takashi; Tawarada, Ryuya; Ohkubo, Akihiro; Sekine, Mitsuo; Seio, Kohji
2008-07-30
New nucleotide pairs applicable to formation of DNA triplexes were developed. We designed oligonucleotides incorporating 5-aryl deoxycytidine derivatives (dC5Ars) and cyclic deoxycytidine derivatives, dCPPP and dCPPI, having an expanded aromatic area, as the second strand. As pairing partners, two types of abasic residues (C3: propylene linker, phi: abasic base) were chosen. It was concluded that, when the 5-aryl-modified cytosine bases paired with the abasic sites in TFOs in a space-fitting manner, the stability of the resulting triplexes significantly increased. The recognition of C3 toward dC5Ars was selective because of the stacking interactions between their aromatic part and the nucleobases flanking the abasic site. These results indicate the potential utility of new nucleotide triplets for DNA triplex formation, which might expand the variety of structures and sequences and might be useful for biorelated fields such as DNA nanotechnologies. PMID:18611007
Nonlinear a Tollmien-Schlichting/vortex interaction in boundary layers
NASA Technical Reports Server (NTRS)
Hall, P.; Smith, F. T.
1989-01-01
The nonlinear reaction between two oblique three-dimensional Tollmien-Schlichting (TS) waves and their induced streamwise-vortex flow is considered theoretically for an incompressible boundary layer. The same theory applies to the destabilization of an incident vortex motion by subharmonic TS waves, followed by interaction. The scales and flow structure involved are addressed for high Reynolds numbers. The nonlinear interaction is powerful, starting at quite low amplitudes with a triple-deck structure for the TS waves but a large-scale structure for the induced vortex, after which strong nonlinear amplification occurs. This includes nonparallel-flow effects. The nonlinear interaction is governed by a partial differential system for the vortex flow coupled with an ordinary-differential one for the TS pressure. The solution properties found sometimes produce a breakup within a finite distance and sometimes further downstream, depending on the input amplitudes upstream and on the wave angles, and that then leads to the second stages of interaction associated with higher amplitudes, the main second stages giving either long-scale phenomena significantly affected by nonparallelism or shorter quasi-parallel ones governed by the full nonlinear triple-deck response.
Nonlinearly interacting trapped particle solitons in collisionless plasmas
NASA Astrophysics Data System (ADS)
Mandal, Debraj; Sharma, Devendra
2016-02-01
The formulation of collective waves in collisionless plasmas is complicated by the kinetic effects produced by the resonant particles, capable of responding to the smallest of the amplitude disturbance. The dispersive plasma manifests this response by generating coherent nonlinear structures associated with phase-space vortices, or holes, at very small amplitudes. The nonlinear interaction between solitary electron phase-space holes is studied in the electron acoustic regime of a collisionless plasma using Vlasov simulations. Evolution of the analytic trapped particle solitary solutions is examined, observing them propagate stably, preserve their identity across strong mutual interactions in adiabatic processes, and display close correspondence with observable processes in nature.
Nonlinear Bubble Interactions in Acoustic Pressure Fields
NASA Technical Reports Server (NTRS)
Barbat, Tiberiu; Ashgriz, Nasser; Liu, Ching-Shi
1996-01-01
The systems consisting of a two-phase mixture, as clouds of bubbles or drops, have shown many common features in their responses to different external force fields. One of particular interest is the effect of an unsteady pressure field applied to these systems, case in which the coupling of the vibrations induced in two neighboring components (two drops or two bubbles) may result in an interaction force between them. This behavior was explained by Bjerknes by postulating that every body that is moving in an accelerating fluid is subjected to a 'kinetic buoyancy' equal with the product of the acceleration of the fluid multiplied by the mass of the fluid displaced by the body. The external sound wave applied to a system of drops/bubbles triggers secondary sound waves from each component of the system. These secondary pressure fields integrated over the surface of the neighboring drop/bubble may result in a force additional to the effect of the primary sound wave on each component of the system. In certain conditions, the magnitude of these secondary forces may result in significant changes in the dynamics of each component, thus in the behavior of the entire system. In a system containing bubbles, the sound wave radiated by one bubble at the location of a neighboring one is dominated by the volume oscillation mode and its effects can be important for a large range of frequencies. The interaction forces in a system consisting of drops are much smaller than those consisting of bubbles. Therefore, as a first step towards the understanding of the drop-drop interaction subject to external pressure fluctuations, it is more convenient to study the bubble interactions. This paper presents experimental results and theoretical predictions concerning the interaction and the motion of two levitated air bubbles in water in the presence of an acoustic field at high frequencies (22-23 KHz).
Mondal, Manas; Halder, Sukanya; Chakrabarti, Jaydeb; Bhattacharyya, Dhananjay
2016-04-01
Stacking interaction between the aromatic heterocyclic bases plays an important role in the double helical structures of nucleic acids. Considering the base as rigid body, there are total of 18 degrees of freedom of a dinucleotide step. Some of these parameters show sequence preferences, indicating that the detailed atomic interactions are important in the stacking. Large variants of non-canonical base pairs have been seen in the crystallographic structures of RNA. However, their stacking preferences are not thoroughly deciphered yet from experimental results. The current theoretical approaches use either the rigid body degrees of freedom where the atomic information are lost or computationally expensive all atom simulations. We have used a hybrid simulation approach incorporating Monte-Carlo Metropolis sampling in the hyperspace of 18 stacking parameters where the interaction energies using AMBER-parm99bsc0 and CHARMM-36 force-fields were calculated from atomic positions. We have also performed stacking energy calculations for structures from Monte-Carlo ensemble by Dispersion corrected density functional theory. The available experimental data with Watson-Crick base pairs are compared to establish the validity of the method. Stacking interaction involving A:U and G:C base pairs with non-canonical G:U base pairs also were calculated and showed that these structures were also sequence dependent. This approach could be useful to generate multiscale modeling of nucleic acids in terms of coarse-grained parameters where the atomic interactions are preserved. This method would also be useful to predict structure and dynamics of different base pair steps containing non Watson-Crick base pairs, as found often in the non-coding RNA structures. © 2015 Wiley Periodicals, Inc. Biopolymers 105: 212-226, 2016. PMID:26600167
Nonlinear Tollmien-Schlichting/vortex interaction in boundary layers
NASA Technical Reports Server (NTRS)
Hall, P.; Smith, F. T.
1988-01-01
The nonlinear reaction between two oblique 3-D Tollmein-Schlichting (TS) waves and their induced streamwise-vortex flow is considered theoretically for an imcompressible boundary layer. The same theory applies to the destabilization of an incident vortex motion by subharmonic TS waves, followed by interaction. The scales and flow structure involved are addressed for high Reynolds numbers. The nonlionear interaction is powerful, starting at quite low amplitudes with a triple-deck structure for the TS waves but a large-scale structure for the induced vortex, after which strong nonlinear amplification occurs. This includes nonparallel-flow effects. The nonlinear interaction is governed by a partial differential system for the vortex flow coupled with an ordinary-differential one for the TS pressure. The solution properties found sometimes produce a breakup within a finite distance and sometimes further downstream, depending on the input amplitudes upstream and on the wave angles, and that then leads to the second stages of interaction associated with higher amplitudes, the main second stages giving either long-scale phenomena significantly affected by nonparallelism or shorter quasi-parallel ones governed by the full nonlinear triple-deck response.
The report gives results of a literature survey of the nonwater quality impacts of closed-cycle cooling systems. Following discussions of cooling tower and stack gas plumes, interactions of these plumes are considered. For cooling tower plumes, plume types, behavior, salt drift g...
Nonlinear light-matter interactions in engineered optical media
NASA Astrophysics Data System (ADS)
Litchinitser, Natalia
In this talk, we consider fundamental optical phenomena at the interface of nonlinear and singular optics in artificial media, including theoretical and experimental studies of linear and nonlinear light-matter interactions of vector and singular optical beams in metamaterials. We show that unique optical properties of metamaterials open unlimited prospects to ``engineer'' light itself. Thanks to their ability to manipulate both electric and magnetic field components, metamaterials open new degrees of freedom for tailoring complex polarization states and orbital angular momentum (OAM) of light. We will discuss several approaches to structured light manipulation on the nanoscale using metal-dielectric, all-dielectric and hyperbolic metamaterials. These new functionalities, including polarization and OAM conversion, beam magnification and de-magnification, and sub-wavelength imaging using novel non-resonant hyperlens are likely to enable a new generation of on-chip or all-fiber structured light applications. The emergence of metamaterials also has a strong potential to enable a plethora of novel nonlinear light-matter interactions and even new nonlinear materials. In particular, nonlinear focusing and defocusing effects are of paramount importance for manipulation of the minimum focusing spot size of structured light beams necessary for nanoscale trapping, manipulation, and fundamental spectroscopic studies. Colloidal suspensions offer as a promising platform for engineering polarizibilities and realization of large and tunable nonlinearities. We will present our recent studies of the phenomenon of spatial modulational instability leading to laser beam filamentation in an engineered soft-matter nonlinear medium. Finally, we introduce so-called virtual hyperbolic metamaterials formed by an array of plasma channels in air as a result of self-focusing of an intense laser pulse, and show that such structure can be used to manipulate microwave beams in a free space. This
Study of solar wind spectra by nonlinear waves interaction
NASA Astrophysics Data System (ADS)
Dwivedi, Navin; Sharma, Rampal; Narita, Yasuhito
2014-05-01
The nature of small-scale turbulent fluctuations in the solar wind (SW) turbulence is a topic that is being investigated extensively nowadays, both theoretically and observationally. Although recent observations predict the evidence of the dominance of kinetic Alfvén waves (KAW) at sub-ion scales with frequency below than ion cyclotron frequency, while other studies suggest that the KAW mode cannot carry the turbulence cascade down to electron scales and that the whistler mode is more relevant. In the present work, nonlinear interaction of kinetic Alfvén wave with whistler wave is considered as one of the possible cause responsible for the solar wind turbulence. A set of coupled dimensionless equations are derived for the intermediate beta plasmas and the nonlinear interaction between these two wave modes has been studied. As a consequence of ponderomotive nonlinearity, the pump KAW becomes filamented when its power exceeds the threshold for the filamentation instability. Whistler is considered to be weak and thus doesn't have enough intensity to initiate its own localization. It gets localized while propagating through the density channel created by KAW localization. In addition, spectral scales of power spectra of KAW and whistler are also calculated. The steeper spectra are found with scaling greater than -5/3. This type of nonlinear interaction between different wave modes and steeper spectra is one of the reasons for the solar wind turbulence and particles acceleration. This work is partially supported by DST (India) and FP7/STORM (313038)
Nonlinear interactions isolated through scale synthesis in experimental wall turbulence
NASA Astrophysics Data System (ADS)
Duvvuri, Subrahmanyam; McKeon, Beverley
2016-07-01
An experimental investigation of nonlinear scale interactions in a forced turbulent boundary layer is presented here. A dynamic wall perturbation mechanism was used to externally force two distinct large-scale synthetic modes with well-defined spatial and temporal wave numbers in a fully turbulent flow. The focus is on characterizing the nonlinear flow response at triadically consistent wave numbers that arises from the direct interactions of the two synthetic modes. These experimental results isolate triadic scale interactions in wall turbulence in a unique fashion, and provide the ability to explore the dynamics of scale coupling in a systematic and detailed manner. The ideas advanced here are intended to contribute towards modeling efforts of high-Reynolds-number wall turbulence.
LINEAR AND NONLINEAR CORRECTIONS IN THE RHIC INTERACTION REGIONS.
PILAT,F.; CAMERON,P.; PTITSYN,V.; KOUTCHOUK,J.P.
2002-06-02
A method has been developed to measure operationally the linear and non-linear effects of the interaction region triplets, that gives access to the multipole content through the action kick, by applying closed orbit bumps and analysing tune and orbit shifts. This technique has been extensively tested and used during the RHIC operations in 2001. Measurements were taken at 3 different interaction regions and for different focusing at the interaction point. Non-linear effects up to the dodecapole have been measured as well as the effects of linear, sextupolar and octupolar corrections. An analysis package for the data processing has been developed that through a precise fit of the experimental tune shift data (measured by a phase lock loop technique to better than 10{sup -5} resolution) determines the multipole content of an IR triplet.
Cross-scale interactions, nonlinearities, and forecasting catastrophic events
Peters, Debra P. C.; Pielke, Roger A.; Bestelmeyer, Brandon T.; Allen, Craig D.; Munson-McGee, Stuart; Havstad, Kris M.
2004-01-01
Catastrophic events share characteristic nonlinear behaviors that are often generated by cross-scale interactions and feedbacks among system elements. These events result in surprises that cannot easily be predicted based on information obtained at a single scale. Progress on catastrophic events has focused on one of the following two areas: nonlinear dynamics through time without an explicit consideration of spatial connectivity [Holling, C. S. (1992) Ecol. Monogr. 62, 447–502] or spatial connectivity and the spread of contagious processes without a consideration of cross-scale interactions and feedbacks [Zeng, N., Neeling, J. D., Lau, L. M. & Tucker, C. J. (1999) Science 286, 1537–1540]. These approaches rarely have ventured beyond traditional disciplinary boundaries. We provide an interdisciplinary, conceptual, and general mathematical framework for understanding and forecasting nonlinear dynamics through time and across space. We illustrate the generality and usefulness of our approach by using new data and recasting published data from ecology (wildfires and desertification), epidemiology (infectious diseases), and engineering (structural failures). We show that decisions that minimize the likelihood of catastrophic events must be based on cross-scale interactions, and such decisions will often be counterintuitive. Given the continuing challenges associated with global change, approaches that cross disciplinary boundaries to include interactions and feedbacks at multiple scales are needed to increase our ability to predict catastrophic events and develop strategies for minimizing their occurrence and impacts. Our framework is an important step in developing predictive tools and designing experiments to examine cross-scale interactions. PMID:15469919
Non-linear wave interaction in a plasma column
NASA Technical Reports Server (NTRS)
Larsen, J.-M.; Crawford, F. W.
1979-01-01
Non-linear three-wave interaction is analysed for propagation along a cylindrical plasma column surrounded by an infinite dielectric, in the absence of a static magnetic field. An averaged-Lagrangian method is used, and the results are specialized to parametric interaction and mode conversion, assuming an undepleted pump wave. The theory for these two types of interactions is extended to include imperfect synchronism, and the effects of loss. Computations are presented indicating that parametric growth rates of the order of a fraction of a decibel per centimeter should be obtainable for plausible laboratory plasma column parameters.
Nonlinear modal interactions in parity-time (PT) symmetric lasers
NASA Astrophysics Data System (ADS)
Ge, Li; El-Ganainy, Ramy
2016-05-01
Parity-time symmetric lasers have attracted considerable attention lately due to their promising applications and intriguing properties, such as free spectral range doubling and single-mode lasing. In this work we discuss nonlinear modal interactions in these laser systems under steady state conditions, and we demonstrate that several gain clamping scenarios can occur for lasing operation in the -symmetric and -broken phases. In particular, we show that, depending on the system’s design and the external pump profile, its operation in the nonlinear regime falls into two different categories: in one the system is frozen in the phase space as the applied gain increases, while in the other the system is pulled towards its exceptional point. These features are first illustrated by a coupled mode formalism and later verified by employing the Steady-state Ab-initio Laser Theory (SALT). Our findings shine light on the robustness of single-mode operation against saturation nonlinearity in -symmetric lasers.
Nonlinear modal interactions in parity-time (PT) symmetric lasers.
Ge, Li; El-Ganainy, Ramy
2016-01-01
Parity-time symmetric lasers have attracted considerable attention lately due to their promising applications and intriguing properties, such as free spectral range doubling and single-mode lasing. In this work we discuss nonlinear modal interactions in these laser systems under steady state conditions, and we demonstrate that several gain clamping scenarios can occur for lasing operation in the -symmetric and -broken phases. In particular, we show that, depending on the system's design and the external pump profile, its operation in the nonlinear regime falls into two different categories: in one the system is frozen in the phase space as the applied gain increases, while in the other the system is pulled towards its exceptional point. These features are first illustrated by a coupled mode formalism and later verified by employing the Steady-state Ab-initio Laser Theory (SALT). Our findings shine light on the robustness of single-mode operation against saturation nonlinearity in -symmetric lasers. PMID:27143324
Li, Jianqiang; Lu, Caijiang; Xu, Changbao; Zhong, Ming
2015-09-01
This paper develops a simple miniature magnetoelectric (ME) laminate FeCuNbSiB/PZT-stack made up of magnetostrictive Fe73.5Cu1Nb3Si13.5B9 (FeCuNbSiB) foils and piezoelectric Pb(Zr, Ti)O3 (PZT) multilayer stack vibrator. Resonant ME interactions of FeCuNbSiB/PZT-stack with different layers of FeCuNbSiB foil (L) are investigated in detail. The experimental results show that the ME voltage coefficient reaches maximum value of 141.5 (V/cm Oe) for FeCuNbSiB/PZT-stack with L = 6. The AC-magnetic sensitivities can reach 524.29 mV/Oe and 1.8 mV/Oe under resonance 91.6 kHz and off-resonance 1 kHz, respectively. The FeCuNbSiB/PZT-stack can distinguish small dc-magnetic field of ∼9 nT. The results indicate that the proposed ME composites are very promising for the cheap room-temperature magnetic field sensing technology. PMID:26429496
NASA Astrophysics Data System (ADS)
Li, Jianqiang; Lu, Caijiang; Xu, Changbao; Zhong, Ming
2015-09-01
This paper develops a simple miniature magnetoelectric (ME) laminate FeCuNbSiB/PZT-stack made up of magnetostrictive Fe73.5Cu1Nb3Si13.5B9 (FeCuNbSiB) foils and piezoelectric Pb(Zr, Ti)O3 (PZT) multilayer stack vibrator. Resonant ME interactions of FeCuNbSiB/PZT-stack with different layers of FeCuNbSiB foil (L) are investigated in detail. The experimental results show that the ME voltage coefficient reaches maximum value of 141.5 (V/cm Oe) for FeCuNbSiB/PZT-stack with L = 6. The AC-magnetic sensitivities can reach 524.29 mV/Oe and 1.8 mV/Oe under resonance 91.6 kHz and off-resonance 1 kHz, respectively. The FeCuNbSiB/PZT-stack can distinguish small dc-magnetic field of ˜9 nT. The results indicate that the proposed ME composites are very promising for the cheap room-temperature magnetic field sensing technology.
He, Lei; Ma, Dongxin; Duan, Lian; Wei, Yongge; Qiao, Juan; Zhang, Deqiang; Dong, Guifang; Wang, Liduo; Qiu, Yong
2012-04-16
Intramolecular π-π stacking interaction in one kind of phosphorescent cationic iridium complexes has been controlled through fluorination of the pendant phenyl rings on the ancillary ligands. Two blue-green-emitting cationic iridium complexes, [Ir(ppy)(2)(F2phpzpy)]PF(6) (2) and [Ir(ppy)(2)(F5phpzpy)]PF(6) (3), with the pendant phenyl rings on the ancillary ligands substituted with two and five fluorine atoms, respectively, have been synthesized and compared to the parent complex, [Ir(ppy)(2)(phpzpy)]PF(6) (1). Here Hppy is 2-phenylpyridine, F2phpzpy is 2-(1-(3,5-difluorophenyl)-1H-pyrazol-3-yl)pyridine, F5phpzpy is 2-(1-pentafluorophenyl-1H-pyrazol-3-yl)-pyridine, and phpzpy is 2-(1-phenyl-1H-pyrazol-3-yl)pyridine. Single crystal structures reveal that the pendant phenyl rings on the ancillary ligands stack to the phenyl rings of the ppy ligands, with dihedral angles of 21°, 18°, and 5.0° between least-squares planes for complexes 1, 2, and 3, respectively, and centroid-centroid distances of 3.75, 3.65, and 3.52 Å for complexes 1, 2, and 3, respectively, indicating progressively reinforced intramolecular π-π stacking interactions from complexes 1 to 2 and 3. Compared to complex 1, complex 3 with a significantly reinforced intramolecular face-to-face π-π stacking interaction exhibits a significantly enhanced (by 1 order of magnitude) photoluminescent efficiency in solution. Theoretical calculations reveal that in complex 3 it is unfavorable in energy for the pentafluorophenyl ring to swing by a large degree and the intramolecular π-π stacking interaction remains on the lowest triplet state. PMID:22462475
Structure of Musashi1 in a complex with target RNA: the role of aromatic stacking interactions.
Ohyama, Takako; Nagata, Takashi; Tsuda, Kengo; Kobayashi, Naohiro; Imai, Takao; Okano, Hideyuki; Yamazaki, Toshio; Katahira, Masato
2012-04-01
Mammalian Musashi1 (Msi1) is an RNA-binding protein that regulates the translation of target mRNAs, and participates in the maintenance of cell 'stemness' and tumorigenesis. Msi1 reportedly binds to the 3'-untranslated region of mRNA of Numb, which encodes Notch inhibitor, and impedes initiation of its translation by competing with eIF4G for PABP binding, resulting in triggering of Notch signaling. Here, the mechanism by which Msi1 recognizes the target RNA sequence using its Ribonucleoprotein (RNP)-type RNA-binding domains (RBDs), RBD1 and RBD2 has been revealed on identification of the minimal binding RNA for each RBD and determination of the three-dimensional structure of the RBD1:RNA complex. Unique interactions were found for the recognition of the target sequence by Msi1 RBD1: adenine is sandwiched by two phenylalanines and guanine is stacked on the tryptophan in the loop between β1 and α1. The minimal recognition sequences that we have defined for Msi1 RBD1 and RBD2 have actually been found in many Msi1 target mRNAs reported to date. The present study provides molecular clues for understanding the biology involving Musashi family proteins. PMID:22140116
NASA Astrophysics Data System (ADS)
Ma, Chunlin; Sun, Junshan; Zhang, Rufen
2007-05-01
Two new trinuclear mono-organooxotin(IV) complexes with 2,3,4,5-tetrafluorobenzoic acid and sodium perchlorate of the types: [(SnR) 3(OH)(2,3,4,5-F 4C 6HCO 2) 4 · ClO 4] · [O 2CC 6HF 4](R = PhCH 2, 1; o- F-PhCH 2 for 2), have been solvothermally synthesized and structurally characterized by elemental, IR, 1H, 13C and 119Sn NMR and X-ray crystallography diffraction analyses. Complex 2 is also characterized by X-ray crystallography diffraction analyses. In complex 2, four carboxyl groups and a perchlorate bridged three tin atoms in a cyclohexane chair arrangement and form the basic framework. A hydroxyl group comprises the oxygen components of the stannoxane ring system. In these complexes, weak but significant intramolecular hydrogen bonding and π-π stacking interaction are also shown. These contacts lead to aggregation and supramolecular assembly of complexes 1 and 2 into 1D or 2D framework.
Effect of nonlinear electromechanical interaction upon wind power generator behavior
NASA Astrophysics Data System (ADS)
Selyutskiy, Yury D.; Klimina, Liubov A.
2014-12-01
A mathematical model is developed for describing a small horizontal axis wind turbine with electric generator, such that the electromechanical interaction is non-linear in current. Dependence of steady regimes of the system upon parameters of the model is studied. In particular, it is shown that increase of wind speed causes qualitative restructuring of the set of steady regimes, which leads to considerable change in behavior of the wind power generator. The proposed model is verified against data obtained in experiments.
Enhanced nonlinear interactions in quantum optomechanics via mechanical amplification
Lemonde, Marc-Antoine; Didier, Nicolas; Clerk, Aashish A.
2016-01-01
The quantum nonlinear regime of optomechanics is reached when nonlinear effects of the radiation pressure interaction are observed at the single-photon level. This requires couplings larger than the mechanical frequency and cavity-damping rate, and is difficult to achieve experimentally. Here we show how to exponentially enhance the single-photon optomechanical coupling strength using only additional linear resources. Our method is based on using a large-amplitude, strongly detuned mechanical parametric drive to amplify mechanical zero-point fluctuations and hence enhance the radiation pressure interaction. It has the further benefit of allowing time-dependent control, enabling pulsed schemes. For a two-cavity optomechanical set-up, we show that our scheme generates photon blockade for experimentally accessible parameters, and even makes the production of photonic states with negative Wigner functions possible. We discuss how our method is an example of a more general strategy for enhancing boson-mediated two-particle interactions and nonlinearities. PMID:27108814
Nonlinear interaction of atmospheric, surface-gravity, and hydroacoustic waves
NASA Astrophysics Data System (ADS)
Kadri, Usama
2016-04-01
We discuss the generation of hydroacoustic waves by the mutual interaction of atmospheric and surface-gravity waves, through nonlinear resonant triad interaction. To this end, we consider a two fluid problem, with a half-space air layer over a compressible water layer of finite depth, and a rigid bottom. The governing equations comprise a quadratic compressible wave equation, and the standard associated boundary conditions. Using a multiple scale approach we derive at the amplitude evolution equations for all three triad members. It is shown that the energy input by the atmospheric wave is transferred to the acoustic mode, with no noticeable effect on the surface gravity mode.
A nonlinear Bloch model for Coulomb interaction in quantum dots
Bidegaray-Fesquet, Brigitte Keita, Kole
2014-02-15
In this paper, we first derive a Coulomb Hamiltonian for electron–electron interaction in quantum dots in the Heisenberg picture. Then we use this Hamiltonian to enhance a Bloch model, which happens to be nonlinear in the density matrix. The coupling with Maxwell equations in case of interaction with an electromagnetic field is also considered from the Cauchy problem point of view. The study is completed by numerical results and a discussion about the advisability of neglecting intra-band coherences, as is done in part of the literature.
Dynamical Nonlinear Interactions of Solids with Strong Terahertz Pulses
NASA Astrophysics Data System (ADS)
Hirori, Hideki; Tanaka, Koichiro
2016-08-01
Table-top high-power terahertz (THz) pulse sources based on the femtosecond lasers are able to reveal fascinating nonlinear transport phenomena in materials and coherently drive low-energy transitions into the nonperturbative nonlinear regime. This article summarizes recent studies on THz nonlinear interactions with solid materials as follows. The tilted-pump-intensity-front scheme uses a LiNbO3 crystal to generate high-field single-cycle THz pulses with a 1 MV/cm amplitude. Such a high amplitude pulse can cause impact ionization in GaAs that excites electrons from the valence band to the conduction band, leading to exciton luminescence. A narrow-bandwidth THz pulse can be generated by using a chirped-pulse-beating method; this scheme has been used to show that resonant intraexcitonic excitation in GaAs induces a large Autler-Townes splitting. Moreover, nonlinear dynamics of magnetism can be studied by using a metallic split ring resonator to enhance the THz magnetic field.
Nonlinear dynamics of specific DNA-protein interactions
NASA Astrophysics Data System (ADS)
Dwiputra, D.; Hidayat, W.; Khairani, R.; Zen, F. P.
2016-03-01
Interactions between DNA binding protein and specific base pairs of nucleic acid is critical for biological process. We propose a new model of DNA-protein interactions to depict the dynamics of specific DNA-protein interactions. Hydrogen bonds (H-bonds) are, among the other intermolecular interactions in DNA, the most distinctive in term of specificity of molecular bonds. As H-bonds account for specificity, we only consider the dynamics affected by H-bonds between DNA base pairs and H-bonds connecting protein side chains and DNA. The H-bonds are modelled by Morse potentials and coupling terms in the Hamiltonian of coupled oscillators resembling a coupling between planar DNA chain and a protein molecule. In this paper we give a perturbative approach as an attempt for a soliton solution. The solution is in the form of nonlinear travelling wave having the amplitudes satisfying coupled nonlinear Schrodinger equations and is interpreted as the mediator for nonlocal transmittance of biological information in DNA.
Nonlinear transient and chaotic interactions in disc brake squeal
NASA Astrophysics Data System (ADS)
Oberst, S.; Lai, J. C. S.
2015-04-01
In automotive disc-brake squeal, most numerical studies have been focussed on the prediction of unstable vibration modes in the frequency domain using the complex eigenvalue analysis. However, the magnitude of the positive real part of a complex eigenvalue is an unreliable indicator of squeal occurrence. Although nonlinearities have been shown to play a significant role in brake squeal, transient nonlinear time domain analyses have rarely been applied owing to high computational costs. Here the complex eigenvalue analysis, the direct steady-state analysis and the transient nonlinear time domain analysis are applied to an isotropic pad-on-disc finite element model representing a simple model of a brake system. While in this investigation, in-plane pad-mode instabilities are not detected by the complex eigenvalue analysis, the dissipated energy obtained by the direct steady-state analysis of the model subjected to harmonic contact pressure excitation is negative at frequencies of pad modes, indicating a potential for instabilities. Transient nonlinear time domain analysis of the pad and disc dynamics reveal that in-plane pad vibrations excite a dominant out-of-plane disc mode. For intermittently chaotic pad motion, the disc dynamics is quasi-periodic; and for chaotic motion of the pad, a toroidal attractor is found for the disc's out-of-plane motion. Nonlinear interactions between the pad and the disc highlight that different parts in a brake system display different dynamic behaviour and need to be analysed separately. The type II intermittency route to chaos could be the cause for the experimentally observed instantaneous mode squeal.
Effects of nonlinearity on cell-ECM interactions
Wen, Qi; Janmey, Paul A.
2014-01-01
Filamentous biopolymers such as F-actin, vimentin, fibrin and collagen that form networks within the cytoskeleton or the extracellular matrix have unusual rheological properties not present in most synthetic soft materials that are used as cell substrates or scaffolds for tissue engineering. Gels formed by purified filamentous biopolymers are often strain stiffening, with an elastic modulus that can increase an order of magnitude at moderate strains that are relevant to cell and tissue deformation in vivo. This review summarizes some experimental studies of nonlinear rheology in biopolymer gels, discusses possible molecular mechanisms that account for strain stiffening, and explores the possible relevance of non-linear rheology to the interactions between cell and extracellular matrices. PMID:23748051
The collapse of stacking fault tetrahedra by interactions with gliding dislocations.
Matsukawa, Yoshitaka; Osetskiy, Yury N; Stocks, George Malcolm; Zinkle, Steven J
2005-01-01
The collapse of stacking-fault tetrahedra (SFT) by gliding dislocations was observed in in situ straining experiments in a transmission electron microscope (TEM). A stacking-fault tetrahedron was collapsed by intersection with a gliding perfect dislocation: only the base portion divided by the gliding plane of the dislocation annihilated, while the apex portion remained intact. As a result of analysis on evolution of atom configuration induced by intersection with perfect dislocation in SFT, it was found that an unusual atom configuration inevitably appeared in one of the ledges formed on stacking-fault planes, which is traditionally called I-ledge: the atoms on adjacent (111) planes were overlapping each other. The overlapping configuration provides a strong repulsive force, being a conceivable driving force to induce a chain reaction of atom displacements that collapses the SFT base portion.
NASA Technical Reports Server (NTRS)
Lee, Sang Soo
1998-01-01
The non-equilibrium critical-layer analysis of a system of frequency-detuned resonant-triads is presented using the generalized scaling of Lee. It is shown that resonant-triads can interact nonlinearly within the common critical layer when their (fundamental) Strouhal numbers are different by a factor whose magnitude is of the order of the growth rate multiplied by the wavenumber of the instability wave. Since the growth rates of the instability modes become larger and the critical layers become thicker as the instability waves propagate downstream, the frequency-detuned resonant-triads that grow independently of each other in the upstream region can interact nonlinearly in the later downstream stage. In the final stage of the non-equilibrium critical-layer evolution, a wide range of instability waves with the scaled frequencies differing by almost an Order of (l) can nonlinearly interact. Low-frequency modes are also generated by the nonlinear interaction between oblique waves in the critical layer. The system of partial differential critical-layer equations along with the jump equations are presented here. The amplitude equations with their numerical solutions are given in Part 2. The nonlinearly generated low-frequency components are also investigated in Part 2.
NASA Astrophysics Data System (ADS)
Jeong, Joonwoo; Han, Ganghee; Johnson, A. T. Charlie; Lubensky, Tom C.; Collings, Peter J.; Yodh, A. G.
2013-03-01
We report on the homeotropic alignment of the lyotropic chromonic liquid crystal, Sunset Yellow FCF (SSY), using pi-pi stacking interactions between the SSY molecules and (1) thin parylene films or (2) a graphene monolayer. The nematic and columnar phases of SSY molecules arise via self-assembly in water into stacks through non-covalent attractions between the SSY molecules. Interestingly, we find that the same non-covalent interactions between SSY molecules and a parylene or graphene alignment layer lead to homeotropic anchoring of these stacks. The nematic phase of SSY is introduced between two glass substrates coated with parylene films or graphene monolayers, and homeotropic alignment of SSY is confirmed by polarized optical microscopy and conoscopy. Additionally, we observe and can explain the stripe domains that occur during cooling of the sample in this cell, and we consider possible novel applications for homeotropically aligned chromonic liquid crystals. We gratefully acknowledge financial support from the National Science Foundation through NSF DMR-1205463 and UPENN MRSEC DMR-1120901
The Soil Stack: An Interactive Computer Program Describing Basic Soil Science and Soil Degradation.
ERIC Educational Resources Information Center
Cattle, S. R.; And Others
1995-01-01
A computer program dealing with numerous aspects of soil degradation has a target audience of high school and university students (16-20 year olds), and is presented in a series of cards grouped together as stacks. Describes use of the software in Australia. (LZ)
Nonlinear modal interactions in parity-time (PT) symmetric lasers
Ge, Li; El-Ganainy, Ramy
2016-01-01
Parity-time symmetric lasers have attracted considerable attention lately due to their promising applications and intriguing properties, such as free spectral range doubling and single-mode lasing. In this work we discuss nonlinear modal interactions in these laser systems under steady state conditions, and we demonstrate that several gain clamping scenarios can occur for lasing operation in the -symmetric and -broken phases. In particular, we show that, depending on the system’s design and the external pump profile, its operation in the nonlinear regime falls into two different categories: in one the system is frozen in the phase space as the applied gain increases, while in the other the system is pulled towards its exceptional point. These features are first illustrated by a coupled mode formalism and later verified by employing the Steady-state Ab-initio Laser Theory (SALT). Our findings shine light on the robustness of single-mode operation against saturation nonlinearity in -symmetric lasers. PMID:27143324
NASA Astrophysics Data System (ADS)
Huang, Chao-Chun; Wu, Wen-Chin
2010-11-01
We investigate the effect of anisotropic and long-range dipole-dipole interaction (DDI) on the center motions of nonoverlapping Bose-Einstein condensates in bilayer and multilayer stacks. In the bilayer, it is shown analytically that while DDI plays no role in the in-phase modes of center motions of condensates, out-of-phase mode frequency (ωo) depends crucially on the strength of DDI (ad). At the small-ad limit, ωo2(ad)-ωo2(0)∝ad. In the multilayer stack, transverse modes associated with center motions of coupled condensates are found to be optical-phonon-like. At the long-wavelength limit, phonon velocity is proportional to ad.
Mukherjee, Sanchita; Kailasam, Senthilkumar; Bansal, Manju; Bhattacharyya, Dhananjay
2014-01-01
Double helical structures of DNA and RNA are mostly determined by base pair stacking interactions, which give them the base sequence-directed features, such as small roll values for the purine-pyrimidine steps. Earlier attempts to characterize stacking interactions were mostly restricted to calculations on fiber diffraction geometries or optimized structure using ab initio calculations lacking variation in geometry to comment on rather unusual large roll values observed in AU/AU base pair step in crystal structures of RNA double helices. We have generated stacking energy hyperspace by modeling geometries with variations along the important degrees of freedom, roll, and slide, which were chosen via statistical analysis as maximally sequence dependent. Corresponding energy contours were constructed by several quantum chemical methods including dispersion corrections. This analysis established the most suitable methods for stacked base pair systems despite the limitation imparted by number of atom in a base pair step to employ very high level of theory. All the methods predict negative roll value and near-zero slide to be most favorable for the purine-pyrimidine steps, in agreement with Calladine's steric clash based rule. Successive base pairs in RNA are always linked by sugar-phosphate backbone with C3'-endo sugars and this demands C1'-C1' distance of about 5.4 Å along the chains. Consideration of an energy penalty term for deviation of C1'-C1' distance from the mean value, to the recent DFT-D functionals, specifically ωB97X-D appears to predict reliable energy contour for AU/AU step. Such distance-based penalty improves energy contours for the other purine-pyrimidine sequences also. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 107-120, 2014. PMID:23722519
Nonlinear wave interactions in shallow water magnetohydrodynamics of astrophysical plasma
NASA Astrophysics Data System (ADS)
Klimachkov, D. A.; Petrosyan, A. S.
2016-05-01
The rotating magnetohydrodynamic flows of a thin layer of astrophysical and space plasmas with a free surface in a vertical external magnetic field are considered in the shallow water approximation. The presence of a vertical external magnetic field changes significantly the dynamics of wave processes in an astrophysical plasma, in contrast to a neutral fluid and a plasma layer in an external toroidal magnetic field. There are three-wave nonlinear interactions in the case under consideration. Using the asymptotic method of multiscale expansions, we have derived nonlinear equations for the interaction of wave packets: three magneto- Poincare waves, three magnetostrophic waves, two magneto-Poincare and one magnetostrophic waves, and two magnetostrophic and one magneto-Poincare waves. The existence of decay instabilities and parametric amplification is predicted. We show that a magneto-Poincare wave decays into two magneto-Poincare waves, a magnetostrophic wave decays into two magnetostrophic waves, a magneto-Poincare wave decays into one magneto-Poincare and one magnetostrophic waves, and a magnetostrophic wave decays into one magnetostrophic and one magneto-Poincare waves. There are the following parametric amplification mechanisms: the parametric amplification of magneto-Poincare waves, the parametric amplification of magnetostrophic waves, the amplification of a magneto-Poincare wave in the field of a magnetostrophic wave, and the amplification of a magnetostrophic wave in the field of a magneto-Poincare wave. The instability growth rates and parametric amplification factors have been found for the corresponding processes.
Molecular dynamics simulation of complex plasmas: interaction of nonlinear waves
NASA Astrophysics Data System (ADS)
Durniak, Celine; Samsonov, Dmitry
2008-11-01
Complex plasmas consist of micron sized microspheres immersed into ordinary ion-electron plasmas. They exist in solid, liquid, gaseous states and exhibit a range of dynamic phenomena such as waves, solitons, phase transitions, heat transfer. These phenomena can be modelled in complex plasmas at the microscopic or ``molecular'' scale, which is almost impossible in ordinary solids and liquids. We simulate a monolayer complex plasma consisting of 3000 negatively-charged particles (or grains) with the help of molecular dynamics computer simulations. The equations of grain motion are solved using a 5^th order Runge Kutta method taking into account interaction of every grain with each other via a Yukawa potential. The grains are confined more strongly in the vertical direction than in the horizontal. After seeding the grains randomly the code is run until the equilibrium is reached as the grain kinetics energy reduces due to damping force equal to the neutral friction in the experiments and a monolayer crystal lattice is formed. Then we investigate interactions between nonlinear waves in a monolayer strongly coupled complex plasma moving in three dimensions. Different excitations are applied during a short time symmetrically on both sides of the lattice. Structural properties and nonlinear waves characteristics are examined as the pulses propagate across the complex plasma in opposite directions.
Spin-orbit interaction with nonlinear wave functions.
Brozell, S. R.; Shepard, R.; Zhang, Z.; Stanford Univ.
2007-12-01
The computation of the spin-orbit interaction is discussed for electronic wave functions expressed in the new nonlinear expansion form. This form is based on spin eigenfunctions using the graphical unitary group approach (GUGA). The nodes of a Shavitt graph in GUGA are connected by arcs, and a Configuration State Function (CSF) is represented as a walk along arcs from the vacuum node to a head node. The wave function is a linear combination of product functions each of which is a linear combination of all CSFs, wherein each CSF coefficient is a product of nonlinear arc factors. When the spin-orbit interaction is included the Shavitt graph is a union of single-headed Shavitt graphs each with the same total number of electrons and orbitals. Thus spin-orbit Shavitt graphs are multiheaded. For full-CI multiheaded Shavitt graphs, analytic expressions are presented for the number of walks, the number of nodes, the number of arcs, and the number of node pairs in the associated auxiliary pair graph.
NASA Astrophysics Data System (ADS)
Asari, K.; Hetland, O. S.; Fujita, S.; Itakura, M.; Okita, T.
2013-11-01
Molecular dynamics simulations were conducted using a set of six interatomic potentials for FCC metals that differed only in stacking fault energy (SFE), to clarify the effect of SFE on interactions between a dissociated edge dislocation and a void. There are two different types of interaction mechanism: separate depinning of the individual partial dislocations and almost simultaneous depinning of the combined partial dislocations. The interaction mechanism depends on both the SFE and void size, and changes the absolute value of the critical resolved shear stress (CRSS) and its dependence on the SFE. In the separate depinning case, the CRSS is relatively low and is almost independent of the SFE, while in the simultaneous case, the CRSS is increases with SFE. The void size for which the change in interaction mechanism occurs increases with decreasing SFE.
Wang, Ti; Kafle, Tika R.; Kattel, Bhupal; Liu, Qingfeng; Wu, Judy; Chan, Wai-Lun
2016-01-01
The electronic properties of small molecule organic crystals depend heavily on the molecular orientation. For multi-layer organic photovoltaics, it is desirable for the molecules to have a face-on orientation in order to enhance the out-of-plane transport properties. However, it is challenging to grow well-ordered and smooth films with a face-on stacking on conventional substrates such as metals and oxides. In this work, metal-phthalocyanine molecules is used as a model system to demonstrate that two-dimensional crystals such as graphene can serve as a template for growing high quality, ultra-flat organic films with a face-on orientation. Furthermore, the molecule-substrate interaction is varied systematically from strong to weak interaction regime with the interaction strength characterized by ultrafast electron transfer measurements. We find that in order to achieve the optimum orientation and morphology, the molecule-substrate interaction needs to be strong enough to ensure a face-on stacking while it needs to be weak enough to avoid film roughening. PMID:27356623
NASA Astrophysics Data System (ADS)
Wang, Ti; Kafle, Tika R.; Kattel, Bhupal; Liu, Qingfeng; Wu, Judy; Chan, Wai-Lun
2016-06-01
The electronic properties of small molecule organic crystals depend heavily on the molecular orientation. For multi-layer organic photovoltaics, it is desirable for the molecules to have a face-on orientation in order to enhance the out-of-plane transport properties. However, it is challenging to grow well-ordered and smooth films with a face-on stacking on conventional substrates such as metals and oxides. In this work, metal-phthalocyanine molecules is used as a model system to demonstrate that two-dimensional crystals such as graphene can serve as a template for growing high quality, ultra-flat organic films with a face-on orientation. Furthermore, the molecule-substrate interaction is varied systematically from strong to weak interaction regime with the interaction strength characterized by ultrafast electron transfer measurements. We find that in order to achieve the optimum orientation and morphology, the molecule-substrate interaction needs to be strong enough to ensure a face-on stacking while it needs to be weak enough to avoid film roughening.
Wang, Ti; Kafle, Tika R; Kattel, Bhupal; Liu, Qingfeng; Wu, Judy; Chan, Wai-Lun
2016-01-01
The electronic properties of small molecule organic crystals depend heavily on the molecular orientation. For multi-layer organic photovoltaics, it is desirable for the molecules to have a face-on orientation in order to enhance the out-of-plane transport properties. However, it is challenging to grow well-ordered and smooth films with a face-on stacking on conventional substrates such as metals and oxides. In this work, metal-phthalocyanine molecules is used as a model system to demonstrate that two-dimensional crystals such as graphene can serve as a template for growing high quality, ultra-flat organic films with a face-on orientation. Furthermore, the molecule-substrate interaction is varied systematically from strong to weak interaction regime with the interaction strength characterized by ultrafast electron transfer measurements. We find that in order to achieve the optimum orientation and morphology, the molecule-substrate interaction needs to be strong enough to ensure a face-on stacking while it needs to be weak enough to avoid film roughening. PMID:27356623
A look to nonlinear interacting Ghost dark energy cosmology
NASA Astrophysics Data System (ADS)
Khurshudyan, Martiros
2016-07-01
In this paper, we organize a look to nonlinear interacting Ghost dark energy cosmology involving a discussion on the thermodynamics of the Ghost dark energy, when the universe is bounded via the Hubble horizon. One of the ways to study a dark energy model, is to reconstruct thermodynamics of it. Ghost dark energy is one of the models of the dark energy which has an explicitly given energy density as a function of the Hubble parameter. There is an active discussion towards various cosmological scenarios, where the Ghost dark energy interacts with the pressureless cold dark matter (CDM). Recently, various models of the varying Ghost dark energy has been suggested, too. To have a comprehensive understanding of suggested models, we will discuss behavior of the cosmological parameters on parameter-redshift z plane. Some discussion on Om and statefinder hierarchy analysis of these models is presented. Moreover, up to our knowledge, suggested forms of interaction between the Ghost dark energy and cold dark matter (CDM) are new, therefore, within obtained results, we provide new contribution to previously discussed models available in the literature. Our study demonstrates that the forms of the interactions considered in the Ghost dark energy cosmology are not exotic and the justification of this is due to the recent observational data.
Characterizing entanglement entropy produced by nonlinear scalar interactions during inflation
Mazur, Dan; Heyl, Jeremy S.
2009-07-15
The density fluctuations that we observe in the universe today are thought to originate from quantum fluctuations produced during a phase of the early universe called inflation. By evolving a wave function describing two coupled Fourier modes of a scalar field forward through an inflationary epoch, we demonstrate that nonlinear effects can result in a generation of entanglement entropy between modes with different momenta in a scalar field during the inflationary period when just one of the modes is observed. Through this mechanism, the field would experience decoherence and appear more like a classical distribution today; however the mechanism is not sufficiently efficient to explain classicality. We find that the amount of entanglement entropy generated scales roughly as a power law S{proportional_to}{lambda}{sup 1.75}, where {lambda} is the coupling coefficient of the nonlinear potential term. We also investigate how the entanglement entropy scales with the duration of inflation and compare various entanglement measures from the literature with the von Neumann entropy. This demonstration explicitly follows particle creation and interactions between modes; consequently, the mechanism contributing to the generation of the von Neumann entropy can be easily seen.
Interaction of highly nonlinear solitary waves with linear elastic media
NASA Astrophysics Data System (ADS)
Yang, Jinkyu; Silvestro, Claudio; Khatri, Devvrath; de Nardo, Luigi; Daraio, Chiara
2011-04-01
We study the interaction of highly nonlinear solitary waves propagating in granular crystals with an adjacent linear elastic medium. We investigate the effects of interface dynamics on the reflection of incident waves and on the formation of primary and secondary reflected waves. Experimental tests are performed to correlate the linear medium geometry, materials, and mass with the formation and propagation of reflected waves. We compare the experimental results with theoretical analysis based on the long-wavelength approximation and with numerical predictions obtained from discrete particle models. Experimental results are found to be in agreement with theoretical analysis and numerical simulations. This preliminary study establishes the foundation for utilizing reflected solitary waves as novel information carriers in nondestructive evaluation of elastic material systems.
Interaction of highly nonlinear solitary waves with linear elastic media.
Yang, Jinkyu; Silvestro, Claudio; Khatri, Devvrath; De Nardo, Luigi; Daraio, Chiara
2011-04-01
We study the interaction of highly nonlinear solitary waves propagating in granular crystals with an adjacent linear elastic medium. We investigate the effects of interface dynamics on the reflection of incident waves and on the formation of primary and secondary reflected waves. Experimental tests are performed to correlate the linear medium geometry, materials, and mass with the formation and propagation of reflected waves. We compare the experimental results with theoretical analysis based on the long-wavelength approximation and with numerical predictions obtained from discrete particle models. Experimental results are found to be in agreement with theoretical analysis and numerical simulations. This preliminary study establishes the foundation for utilizing reflected solitary waves as novel information carriers in nondestructive evaluation of elastic material systems. PMID:21599325
Nonlinear Laser-Plasma Interaction in Magnetized Liner Inertial Fusion
Geissel, Matthias; Awe, Thomas James; Bliss, David E.; Campbell, Edward Michael; Gomez, Matthew R.; Harding, Eric; Harvey-Thompson, Adam James; Hansen, Stephanie B.; Jennings, Christopher Ashley; Kimmel, Mark W.; et al
2016-03-04
Sandia National Laboratories is pursuing a variation of Magneto-Inertial Fusion called Magnetized Liner Inertial Fusion, or MagLIF. The MagLIF approach requires magnetization of the deuterium fuel, which is accomplished by an initial external B-Field and laser-driven pre-heat. Although magnetization is crucial to the concept, it is challenging to couple sufficient energy to the fuel, since laser-plasma instabilities exist, and a compromise between laser spot size, laser entrance window thickness, and fuel density must be found. Ultimately, nonlinear processes in laser plasma interaction, or laser-plasma instabilities (LPI), complicate the deposition of laser energy by enhanced absorption, backscatter, filamentation and beam-spray. Wemore » determine and discuss key LPI processes and mitigation methods. Results with and without improvement measures are presented.« less
Nonlinear laser-plasma interaction in magnetized liner inertial fusion
NASA Astrophysics Data System (ADS)
Geissel, Matthias; Awe, T. J.; Bliss, D. E.; Campbell, M. E.; Gomez, M. R.; Harding, E.; Harvey-Thompson, A. J.; Hansen, S. B.; Jennings, C.; Kimmel, M. W.; Knapp, P.; Lewis, S. M.; McBride, R. D.; Peterson, K.; Schollmeier, M.; Scoglietti, D. J.; Sefkow, A. B.; Shores, J. E.; Sinars, D. B.; Slutz, S. A.; Smith, I. C.; Speas, C. S.; Vesey, R. A.; Porter, J. L.
2016-03-01
Sandia National Laboratories is pursuing a variation of Magneto-Inertial Fusion called Magnetized Liner Inertial Fusion, or MagLIF. The MagLIF approach requires magnetization of the deuterium fuel, which is accomplished by an initial external B-Field and laser-driven pre-heat. While magnetization is crucial to the concept, it is challenging to couple sufficient energy to the fuel, since laser-plasma instabilities exist, and a compromise between laser spot size, laser entrance window thickness, and fuel density must be found. Nonlinear processes in laser plasma interaction, or laser-plasma instabilities (LPI), complicate the deposition of laser energy by enhanced absorption, backscatter, filamentation and beam-spray. Key LPI processes are determined, and mitigation methods are discussed. Results with and without improvement measures are presented.
On a class of nonlinear dispersive-dissipative interactions
Rosenau, P.
1997-07-29
The authors study the prototypical, genuinely nonlinear, equation; u{sub t} + a(u{sup m}){sub x} + (u{sup n}){sub xxx} = {mu}(u{sup k}){sub xx}, a, {mu} = consts., which encompasses a wide variety of dissipative-dispersive interactions. The parametric surface k = (m + n)/2 separates diffusion dominated from dissipation dominated phenomena. On this surface dissipative and dispersive effects are in detailed balance for all amplitudes. In particular, the m = n + 2 = k + 1 subclass can be transformed into a form free of convection and dissipation making it accessible to theoretical studies. Both bounded and unbounded oscillations are found and certain exact solutions are presented. When a = (2{mu}3/){sup 2} the map yields a linear equation; rational, periodic and aperiodic solutions are constructed.
Topological charge algebra of optical vortices in nonlinear interactions
NASA Astrophysics Data System (ADS)
Shutova, Mariia; Zhdanova, Alexandra; Bahari, Aysan; Zhi, Miaochan; Sokolov, Alexei
2016-05-01
Optical vortices find their use in multiple areas of research and technology; in particular, they provide an opportunity to generate short-pulse spatially-structured optical beams, which can be used to study ultrafast processes. In our work, we explore interactions of femtosecond optical vortices in nonlinear crystals. We investigate the transfer of orbital angular momentum among multiple (applied and generated) beams involved in a coherent Raman interaction. We use a liquid crystal light modulator to shape the applied pump and Stokes beams into optical vortices with various integer values of topological charge, and cross them in a Raman-active crystal to produce multiple Stokes and anti-Stokes sidebands. We then examine the transfer of optical angular momentum into each sideband and find that it follows a certain law that can be derived from angular momentum conservation for created and annihilated photons, or equivalently, from phase-matching considerations for the interacting beams. Presenter is supported by the Herman F. Heep and Minnie Belle Heep Texas A&M University Endowed Fund administered by the Texas A&M Foundation
NASA Astrophysics Data System (ADS)
Martínez, Enrique; Uberuaga, Blas P.; Beyerlein, Irene J.
2016-02-01
The presence of stacking fault tetrahedra (SFTs) in face-centered-cubic metals substantially modifies the material response to external loading. These defects are extremely stable with increasing energetic stability as they grow in size. At the sizes visible within a transmission electron microscope, they appear nearly immobile. We have recently shown that these defects might indeed migrate, with defective SFTs exhibiting particularly high mobilities. In this paper, using molecular dynamics, we show how mobile SFTs interact with various types of extended defects, including free surfaces, dislocations, and interfaces in Cu and Cu-Nb systems. We observe a direct relation between the energetics of a single vacancy interacting with each external defect and the propensity for the SFT to be absorbed. Finally, using mesoscale modeling, we show how the fact that SFTs can migrate influences the system evolution and potentially important observables of interest such as the void denuded zones around defect sinks.
Nonlinear neutrino-photon interactions inside strong laser pulses
NASA Astrophysics Data System (ADS)
Meuren, Sebastian; Keitel, Christoph H.; Di Piazza, Antonino
2015-06-01
Even though neutrinos are neutral particles and interact only via the exchange of weak gauge bosons, charged leptons and quarks can mediate a coupling to the photon field beyond tree level. Inside a relativistically strong laser field nonlinear effects in the laser amplitude can play an important role, as electrons and positrons interact nonperturbatively with the coherent part of the photon field. Here, we calculate for the first time the leading-order contribution to the axial-vector-vector current-coupling tensor inside an arbitrary plane-wave laser field (which is taken into account exactly by employing the Furry picture). The current-coupling tensor appears in the calculation of various electroweak processes inside strong laser fields like photon emission or trident electron-positron pair production by a neutrino. Moreover, as we will see below, the axial-vector-vector current-coupling tensor contains the Adler-Bell-Jackiw (ABJ) anomaly. This occurrence renders the current-coupling tensor also interesting from a fundamental point of view, as it is the simplest Feynman diagram in an external field featuring this kind of anomaly.
Mukherjee, Sanchita; Kailasam, Senthilkumar; Bansal, Manju; Bhattacharyya, Dhananjay
2015-03-01
Understanding dinucleotide sequence directed structures of nuleic acids and their variability from experimental observation remained ineffective due to unavailability of statistically meaningful data. We have attempted to understand this from energy scan along twist, roll, and slide degrees of freedom which are mostly dependent on dinucleotide sequence using ab initio density functional theory. We have carried out stacking energy analysis in these dinucleotide parameter phase space for all ten unique dinucleotide steps in DNA and RNA using DFT-D by ωB97X-D/6-31G(2d,2p), which appears to satisfactorily explain conformational preferences for AU/AU step in our recent study. We show that values of roll, slide, and twist of most of the dinucleotide sequences in crystal structures fall in the low energy region. The minimum energy regions with large twist values are associated with the roll and slide values of B-DNA, whereas, smaller twist values correspond to higher stability to RNA and A-DNA like conformations. Incorporation of solvent effect by CPCM method could explain the preference shown by some sequences to occur in B-DNA or A-DNA conformations. Conformational preference of BII sub-state in B-DNA is preferentially displayed mainly by pyrimidine-purine steps and partly by purine-purine steps. The purine-pyrimidine steps show largest effect of 5-methyl group of thymine in stacking energy and the introduction of solvent reduces this effect significantly. These predicted structures and variabilities can explain the effect of sequence on DNA and RNA functionality. PMID:25257334
Evidence of π-stacking Interactions in the Self-Assembly of hIAPP22–29†
Profit, Adam A.; Felsen, Valentina; Chinwong, Justina; Mojica, Elmer-Rico E.; Desamero, Ruel Z. B.
2012-01-01
The role aromatic amino acids play in the formation of amyloid is a subject of controversy. In an effort to clarify the contribution of aromaticity to the self-assembly of hIAPP22–29, peptide analogs containing electron donating groups (EDGs) or electron withdrawing groups (EWGs) as substituents on the aromatic ring of Phe-23 at the para position have been synthesized and characterized using turbidity measurements in conjunction with Raman, and fluorescence spectroscopy. Results indicate the incorporation of EDGs on the aromatic ring of Phe-23 virtually abolish the ability of hIAPP22–29 to form amyloid. Peptides containing EWGs were still capable of forming aggregates. These aggregates were found to be rich in β-sheet secondary structure. TEM images of the aggregates confirm the presence of amyloid fibrils. The observed difference in amyloidogenic propensity between peptides containing EDGs and those with EWGs appears not to be based on differences in peptide hydrophobicity. Fluorescence and Raman spectroscopic investigations reveal that the environment surrounding the aromatic ring becomes more hydrophobic and ordered upon aggregation. Furthermore, Raman measurements of peptide analogs containing EWGs, conclusively demonstrate a distinct downshift in the -C=C- ring mode (ca. 1600 cm−1) upon aggregation that has previously been shown to be indicative of π-stacking. While previous work has demonstrated that π-stacking is not an absolute requirement for fibrillization, our findings indicate that Phe-23 also contributes to fibril formation through π-stacking interactions and that it is not only the hydrophobic nature of this residue that is relevant in the self-assembly of hIAPP22–29. PMID:23229921
Nonlinear interactions of electromagnetic waves with the auroral ionosphere
NASA Astrophysics Data System (ADS)
Wong, Alfred Y.
1999-09-01
The ionosphere provides us with an opportunity to perform plasma experiments in an environment with long confinement times, very large-scale lengths, and no confining walls. The auroral ionosphere with its nearly vertical magnetic field geometry is uniquely endowed with large amount of free energy from electron and ion precipitation along the magnetic field and mega-ampere current across the magnetic field. To take advantage of this giant outdoor laboratory, two facilities HAARP and HIPAS, with frequencies ranging from the radio to optical bands, are now available for active probing of and interaction with this interesting region. The ponderomotive pressures from the self-consistent wave fields have produced significant local perturbations of density and particle distributions at heights where the incident EM frequency matches a plasma resonance. This paper will review theory and experiments covering the nonlinear phenomena of parametric decay instability to wave collapse processes. At HF frequencies plasma lenses can be created by preconditioning pulses to focus what is a normally divergent beam into a high-intensity spot to further enhance nonlinear phenomena. At optical wavelengths a large rotating liquid metal mirror is used to focus laser pulses up to a given height. Such laser pulses are tuned to the same wavelengths of selected atomic and molecular resonances, with resulting large scattering cross sections. Ongoing experiments on dual-site experiments and excitation of ELF waves will be presented. The connection of such basic studies to environmental applications will be discussed. Such applications include the global communication using ELF waves, the ozone depletion and remediation and the control of atmospheric CO2 through the use of ion cyclotron resonant heating.
Nonlinear interactions of electromagnetic waves with the auroral ionosphere
Wong, Alfred Y.
1999-09-20
The ionosphere provides us with an opportunity to perform plasma experiments in an environment with long confinement times, very large-scale lengths, and no confining walls. The auroral ionosphere with its nearly vertical magnetic field geometry is uniquely endowed with large amount of free energy from electron and ion precipitation along the magnetic field and mega-ampere current across the magnetic field. To take advantage of this giant outdoor laboratory, two facilities HAARP and HIPAS, with frequencies ranging from the radio to optical bands, are now available for active probing of and interaction with this interesting region. The ponderomotive pressures from the self-consistent wave fields have produced significant local perturbations of density and particle distributions at heights where the incident EM frequency matches a plasma resonance. This paper will review theory and experiments covering the nonlinear phenomena of parametric decay instability to wave collapse processes. At HF frequencies plasma lenses can be created by preconditioning pulses to focus what is a normally divergent beam into a high-intensity spot to further enhance nonlinear phenomena. At optical wavelengths a large rotating liquid metal mirror is used to focus laser pulses up to a given height. Such laser pulses are tuned to the same wavelengths of selected atomic and molecular resonances, with resulting large scattering cross sections. Ongoing experiments on dual-site experiments and excitation of ELF waves will be presented. The connection of such basic studies to environmental applications will be discussed. Such applications include the global communication using ELF waves, the ozone depletion and remediation and the control of atmospheric CO{sub 2} through the use of ion cyclotron resonant heating.
Nečasová, Ivona; Mishra, Sushil Kumar; Komárek, Jan; Koča, Jaroslav
2012-01-01
Carbohydrate – receptor interactions are an integral part of biological events. They play an important role in many cellular processes, such as cell-cell adhesion, cell differentiation and in-cell signaling. Carbohydrates can interact with a receptor by using several types of intermolecular interactions. One of the most important is the interaction of a carbohydrate's apolar part with aromatic amino acid residues, known as dispersion interaction or CH/π interaction. In the study presented here, we attempted for the first time to quantify how the CH/π interaction contributes to a more general carbohydrate - protein interaction. We used a combined experimental approach, creating single and double point mutants with high level computational methods, and applied both to Ralstonia solanacearum (RSL) lectin complexes with α-l-Me-fucoside. Experimentally measured binding affinities were compared with computed carbohydrate-aromatic amino acid residue interaction energies. Experimental binding affinities for the RSL wild type, phenylalanine and alanine mutants were −8.5, −7.1 and −4.1 kcal.mol−1, respectively. These affinities agree with the computed dispersion interaction energy between carbohydrate and aromatic amino acid residues for RSL wild type and phenylalanine, with values −8.8, −7.9 kcal.mol−1, excluding the alanine mutant where the interaction energy was −0.9 kcal.mol−1. Molecular dynamics simulations show that discrepancy can be caused by creation of a new hydrogen bond between the α-l-Me-fucoside and RSL. Observed results suggest that in this and similar cases the carbohydrate-receptor interaction can be driven mainly by a dispersion interaction. PMID:23056230
NASA Astrophysics Data System (ADS)
dos Santos, Renato B.; de Brito Mota, F.; Rivelino, R.; Kakanakova-Georgieva, A.; Gueorguiev, G. K.
2016-04-01
Graphite-like hexagonal AlN (h-AlN) multilayers have been experimentally manifested and theoretically modeled. The development of any functional electronics applications of h-AlN would most certainly require its integration with other layered materials, particularly graphene. Here, by employing vdW-corrected density functional theory calculations, we investigate structure, interaction energy, and electronic properties of van der Waals stacking sequences of few-layer h-AlN with graphene. We find that the presence of a template such as graphene induces enough interlayer charge separation in h-AlN, favoring a graphite-like stacking formation. We also find that the interface dipole, calculated per unit cell of the stacks, tends to increase with the number of stacked layers of h-AlN and graphene.
Nonlinear normal modes modal interactions and isolated resonance curves
Kuether, Robert J.; Renson, L.; Detroux, T.; Grappasonni, C.; Kerschen, G.; Allen, M. S.
2015-05-21
The objective of the present study is to explore the connection between the nonlinear normal modes of an undamped and unforced nonlinear system and the isolated resonance curves that may appear in the damped response of the forced system. To this end, an energy balance technique is used to predict the amplitude of the harmonic forcing that is necessary to excite a specific nonlinear normal mode. A cantilever beam with a nonlinear spring at its tip serves to illustrate the developments. Furthermore, the practical implications of isolated resonance curves are also discussed by computing the beam response to sine sweepmore » excitations of increasing amplitudes.« less
Nonlinear normal modes modal interactions and isolated resonance curves
Kuether, Robert J.; Renson, L.; Detroux, T.; Grappasonni, C.; Kerschen, G.; Allen, M. S.
2015-05-21
The objective of the present study is to explore the connection between the nonlinear normal modes of an undamped and unforced nonlinear system and the isolated resonance curves that may appear in the damped response of the forced system. To this end, an energy balance technique is used to predict the amplitude of the harmonic forcing that is necessary to excite a specific nonlinear normal mode. A cantilever beam with a nonlinear spring at its tip serves to illustrate the developments. Furthermore, the practical implications of isolated resonance curves are also discussed by computing the beam response to sine sweep excitations of increasing amplitudes.
Nonlinear theory of slow cyclotron wave interaction in folded waveguide
Ganguly, A.K.; Choi, J.J.
1995-12-31
A three-dimensional non-linear theory is presented for the generation of broadband radiation from slow cyclotron wave interaction in a folded waveguide. The serpentine structure is formed by folding a rectangular waveguide so that the orientation of the magnetic changes (H-plane bend) instead of the conventional E-plane bend configuration where the orientation of the electric field changes. The H-plane bend structure can use larger beam tunnel without distorting the rf field structure and generate higher output power. Numerical results will be shown for the TE{sub 10} mode propagation in an unridged and a double ridged waveguide. For a 61.5 kV, 3 A beam with {alpha}=1.0 and {Delta}v{sub z}/v{sub z}=0, calculations show an efficiency of 25% with 20% bandwidth and an efficiency of 35% at 10% bandwidth. The efficiency and bandwidth is relatively unchanged up to a beam axial velocity spread of 2%. The bandwidth can be further increased by mode coalescing techniques. Multistage operation is necessary to avoid backward wave oscillation.
NASA Astrophysics Data System (ADS)
Fan, Haidong; Wang, Qingyuan; Ouyang, Chaojun
2015-10-01
The defect-free channels were frequently observed in irradiated materials, i.e. copper, as a result of the stacking fault tetrahedron (SFT) interactions with dislocations. However, the underlying mechanisms for this process are still unclear to date. To address them, a comprehensive study on the interactions between SFTs and mixed dislocations was performed using molecular dynamics simulations. In particular, eight interaction geometries were considered, in terms of the dislocation Burgers vector directions, dislocation gliding directions and intersection positions on SFT. Various interaction outcomes were revealed after dislocation detachment. (1) SFT is fully absorbed through the transformation into Lomer dislocations, and subsequently moves out of free surfaces along the dislocation. (2) SFT is partially absorbed with the absorbed SFT base moving out of free surfaces along the dislocation. (3) SFT is not absorbed but sheared with ledges left on the SFT faces. (4) SFT is unaffected by the mixed dislocation. The current simulations, especially the full SFT absorption, provide important insights into the forming mechanisms of defect-free channels in irradiated materials.
NASA Astrophysics Data System (ADS)
Wang, Lei; Zhu, Yu-Jie; Wang, Zi-Zhe; Qi, Feng-Hua; Guo, Rui
2016-04-01
We present the semirational solution in terms of the determinant form for the derivative nonlinear Schrödinger equation. It describes the nonlinear combinations of breathers and rogue waves (RWs). We show here that the solution appears as a mixture of polynomials with exponential functions. The k-order semirational solution includes k - 1 types of nonlinear superpositions, i.e., the l-order RW and (k-l)-order breather for l = 1 , 2 , … , k - 1 . By adjusting the shift and spectral parameters, we display various patterns of the semirational solutions for describing the interactions among the RWs and breathers. We find that k-order RW can be derived from a l-order RW interacting with 1/2(k - l) (k + l + 1) neighboring elements of a (k - l)-order breather for l = 1 , 2 , … , k - 1 .
Santana, M D; López-Banet, L; Sánchez, G; Pérez, J; Pérez, E; García, L; Serrano, J L; Espinosa, A
2016-05-17
The solution/solid state luminescence properties of selected orthometalated palladium complexes have been investigated in parallel with the relevant structural information provided by their X-ray crystal structures and theoretical calculations. Two cyclometalated backbones with different stacking abilities and a selection of bridging O^O, O^N or N^S ligands comprise the series under study, [{Pd(μ-L) (C^N)}2] (C^N = N-phenylpyrazole (Phpz) ; N-benzylideneaniline (Bza) ; L = acetate (Aco) , succinimidate (succ) , phthalimidate (phthal) , 1-methylimidazoline-2 thionate (Smeimid) ), completed with mononuclear [Pd(C^N)(N-pClPhsal)] (N-pClPhsal = chlorophenylsalycilaldiminate) complexes. New compounds , and were synthesized and the X-ray structures of , , , and have been elucidated in order to examine and compare solid-state Pd(C^N)-Pd(C^N) and ligand-ligand interactions with the rest of the series. The molecular structures of the complexes reveal intramolecular PdPd distances between 2.842 and 2.999 Å and π-π and C-Hπ interactions. All complexes studied show emission in the solid state at room temperature and a relationship is observed between emission energy, the nature of the lowest energy excited state, and metal-metal interactions. DFT calculations are undertaken to gain insight into the relationship between the structure and photophysical properties of the complexes. PMID:27137832
Near-planar TS waves and longitudinal vortices in channel flow - Nonlinear interaction and focussing
NASA Technical Reports Server (NTRS)
Hall, Philip; Smith, Frank T.
1990-01-01
The nonlinear interaction between planar or near-planar Tollmien-Schlichting waves and longitudinal vortices, induced or input, is considered theoretically for channel flows at high Reynolds numbers. Several kinds of nonlinear interaction, dependent on the input amplitudes and wavenumbers or on previously occurring interactions, are found and inter-related. The first, Type 1, is studied the most here and it usually produces spanwise focusing of both the wave and the vortex motion, within a finite scaled time, along with enhancement of both their amplitudes. This then points to the nonlinear interaction Type 2 where new interactive effects come into force to drive the wave and the vortex nonlinearly. Types 3, 4 correspond to still higher amplitudes, with 3 being related to 2, while 4 is connected with a larger-scale interaction 5 studied in an allied paper. Both 3, 4 are subsets of the full three-dimensional triple-deck-lie interaction, 6. The strongest nonlinear interactions are those of 4, 5, 6 since they alter the mean-flow profile substantially, i.e., by an O(1) relative amount. All the types of nonlinear interaction, however, can result in the formation of focused responses in the sense of spanwise concentrations and/or amplifications of vorticity and wave amplitude.
Near-planar TS waves and longitudinal vortices in channel flow: Nonlinear interaction and focusing
NASA Technical Reports Server (NTRS)
Hall, P.; Smith, F. T.
1989-01-01
The nonlinear interaction between planar or near-planar Tollmien-Schlichting waves and longitudinal vortices, induced or input, is considered theoretically for channel flows at high Reynolds numbers. Several kinds of nonlinear interaction, dependent on the input amplitudes and wavenumbers or on previously occurring interactions, are found and inter-related. The first, Type 1, is studied the most here and it usually produces spanwise focusing of both the wave and the vortex motion, within a finite scaled time, along with enhancement of both their amplitudes. This then points to the nonlinear interaction Type 2 where new interactive effects come into force to drive the wave and the vortex nonlinearly. Types 3, 4 correspond to still higher amplitudes, with 3 being related to 2, while 4 is connected with a larger-scale interaction 5 studied in an allied paper. Both 3, 4 are subsets of the full three-dimensional triple-deck-lie interaction, 6. The strongest nonlinear interactions are those of 4, 5, 6 since they alter the mean-flow profile substantially, i.e., by an 0(1) relative amount. All the types of nonlinear interaction however can result in the formation of focussed responses in the sense of spanwise concentrations and/or amplifications of vorticity and wave amplitude.
Reid, Scott A; Nyambo, Silver; Muzangwa, Lloyd; Uhler, Brandon
2013-12-19
Noncovalent interactions play an important role in many chemical and biochemical processes. Building upon our recent study of the homoclusters of chlorobenzene, where π-π stacking and CH/π interactions were identified as the most important binding motifs, in this work we present a study of bromobenzene (PhBr) and mixed bromobenzene-benzene clusters. Electronic spectra in the region of the PhBr monomer S0-S1 (ππ*) transition were obtained using resonant two-photon ionization (R2PI) methods combined with time-of-flight mass analysis. As previously found for related systems, the PhBr cluster spectra show a broad feature whose center is red-shifted from the monomer absorption, and electronic structure calculations indicate the presence of multiple isomers and Franck-Condon activity in low-frequency intermolecular modes. Calculations at the M06-2X/aug-cc-pVDZ level find in total eight minimum energy structures for the PhBr dimer: four π-stacked structures differing in the relative orientation of the Br atoms (denoted D1-D4), one T-shaped structure (D5), and three halogen bonded structures (D6-D8). The calculated binding energies of these complexes, corrected for basis set superposition error (BSSE) and zero-point energy (ZPE), are in the range of -6 to -24 kJ/mol. Time-dependent density functional theory (TDDFT) calculations predict that these isomers absorb over a range that is roughly consistent with the breadth of the experimental spectrum. To examine the influence of dipole-dipole interaction, R2PI spectra were also obtained for the mixed PhBr···benzene dimer, where the spectral congestion is reduced and clear vibrational structure is observed. This structure is well-simulated by Franck-Condon calculations that incorporate the lowest frequency intermolecular modes. Calculations find four minimum energy structures for the mixed dimer and predict that the binding energy of the global minimum is reduced by ~30% relative to the global minimum PhBr dimer
Nonlinear interaction of near-planar TS waves and longitudinal vortices in boundary-layer transition
NASA Technical Reports Server (NTRS)
Smith, F. T.
1988-01-01
The nonlinear interactions that evolve between a planar or nearly planar Tollmien-Schlichting (TS) wave and the associated longitudinal vortices are considered theoretically for a boundary layer at high Reynolds number. The vortex flow is either induced by the TS nonlinear forcing or is input upstream, and similarly for the nonlinear wave development. Three major kinds of nonlinear spatial evolution, Types 1-3, are found. Each can start from secondary instability and then become nonlinear, Type 1 proving to be relatively benign but able to act as a pre-cursor to the Types 2, 3 which turn out to be very powerful nonlinear interactions. Type 2 involves faster stream-wise dependence and leads to a finite-distance blow-up in the amplitudes, which then triggers the full nonlinear 3-D triple-deck response, thus entirely altering the mean-flow profile locally. In contrast, Type 3 involves slower streamwise dependence but a faster spanwise response, with a small TS amplitude thereby causing an enhanced vortex effect which, again, is substantial enough to entirely alter the meanflow profile, on a more global scale. Streak-like formations in which there is localized concentration of streamwise vorticity and/or wave amplitude can appear, and certain of the nonlinear features also suggest by-pass processes for transition and significant changes in the flow structure downstream. The powerful nonlinear 3-D interactions 2, 3 are potentially very relevant to experimental findings in transition.
NASA Astrophysics Data System (ADS)
O'Rourke, Natasha F.; Ronaldson, Michael; Stanley Cameron, T.; Wang, Ruiyao; Aquino, Manuel A. S.
2013-11-01
The synthesis of three new valent-averaged tetracarboxylatodiruthenium (II,III) complexes, [Ru2(1-naphthylacetate)4(H2O)2](PF6)ṡ4THF, 1ṡ4THF, [Ru2(2-naphthoate)4(THF)2](PF6)ṡ3THF, 2ṡ3THF, and [Ru2(coumarin-3-carboxylate)4(MeOH)2](PF6)ṡMeOHṡH2O, 3ṡMeOHṡH2O, was accomplished using a well documented carboxylate exchange reaction. All three complexes were thoroughly characterized using infrared and UV-Vis spectroscopies, elemental analysis and X-ray diffraction. Due to the extended π-systems present, two of the complexes, 2ṡ3THF and 3ṡMeOHṡH2O, display extensive π-stacking in two dimensions, with similar interactions notably absent in 1ṡ4THF due to the perpendicular orientation of the naphthyl rings. Modest H-bonding is seen in complexes 1ṡ4THF and 3ṡMeOHṡH2O. As these types of complexes are noted secondary building units (SBU's) in the construction of metal-organic frameworks (MOF's), the significance of these interactions in stabilizing even larger, supramolecular structures, are noted.
Roberts, G. C.; Ramana, M. V.; Corrigan, C.; Kim, D.; Ramanathan, V.
2008-01-01
Aerosol impacts on climate change are still poorly understood, in part, because the few observations and methods for detecting their effects are not well established. For the first time, the enhancement in cloud albedo is directly measured on a cloud-by-cloud basis and linked to increasing aerosol concentrations by using multiple autonomous unmanned aerial vehicles to simultaneously observe the cloud microphysics, vertical aerosol distribution, and associated solar radiative fluxes. In the presence of long-range transport of dust and anthropogenic pollution, the trade cumuli have higher droplet concentrations and are on average brighter. Our observations suggest a higher sensitivity of radiative forcing by trade cumuli to increases in cloud droplet concentrations than previously reported owing to a constrained droplet radius such that increases in droplet concentrations also increase cloud liquid water content. This aerosol-cloud forcing efficiency is as much as −60 W m−2 per 100% percent cloud fraction for a doubling of droplet concentrations and associated increase of liquid water content. Finally, we develop a strategy for detecting aerosol–cloud interactions based on a nondimensional scaling analysis that relates the contribution of single clouds to albedo measurements and illustrates the significance of characterizing cloud morphology in resolving radiometric measurements. This study demonstrates that aerosol–cloud–albedo interactions can be directly observed by simultaneous observations below, in, and above the clouds. PMID:18499803
Roberts, G C; Ramana, M V; Corrigan, C; Kim, D; Ramanathan, V
2008-05-27
Aerosol impacts on climate change are still poorly understood, in part, because the few observations and methods for detecting their effects are not well established. For the first time, the enhancement in cloud albedo is directly measured on a cloud-by-cloud basis and linked to increasing aerosol concentrations by using multiple autonomous unmanned aerial vehicles to simultaneously observe the cloud microphysics, vertical aerosol distribution, and associated solar radiative fluxes. In the presence of long-range transport of dust and anthropogenic pollution, the trade cumuli have higher droplet concentrations and are on average brighter. Our observations suggest a higher sensitivity of radiative forcing by trade cumuli to increases in cloud droplet concentrations than previously reported owing to a constrained droplet radius such that increases in droplet concentrations also increase cloud liquid water content. This aerosol-cloud forcing efficiency is as much as -60 W m(-2) per 100% percent cloud fraction for a doubling of droplet concentrations and associated increase of liquid water content. Finally, we develop a strategy for detecting aerosol-cloud interactions based on a nondimensional scaling analysis that relates the contribution of single clouds to albedo measurements and illustrates the significance of characterizing cloud morphology in resolving radiometric measurements. This study demonstrates that aerosol-cloud-albedo interactions can be directly observed by simultaneous observations below, in, and above the clouds. PMID:18499803
Two-body problem of core-region coupled magnetic vortex stacks
NASA Astrophysics Data System (ADS)
Hänze, Max; Adolff, Christian F.; Velten, Sven; Weigand, Markus; Meier, Guido
2016-02-01
The dynamics of all four combinations of possible polarity and circularity states in a stack of two vortices is investigated by time-resolved scanning transmission x-ray microscopy. The vortex stacks are excited by unidirectional magnetic fields leading to a collective oscillation. Four different modes are observed that depend on the relative polarizations and circularities of the stacks. They are excited to a driven oscillation. We observe a repulsive and attractive interaction of the vortex cores depending on their relative polarizations. The nonlinearity of this core interaction results in different trajectories that describe a two-body problem.
Zhao, Yuan; Li, Jue; Gu, Hui; Wei, Dongqing; Xu, Yao-Chang; Fu, Wei; Yu, Zhengtian
2015-09-01
π-π Interaction is a direct attractive non-covalent interaction between aromatic moieties, playing an important role in DNA stabilization, drug intercalation, etc. Aromatic rings interact through several different conformations including face-to-face, T-shaped, and offset stacked conformation. Previous quantum calculations indicated that T-shaped and offset stacked conformations are preferred for their smaller electron repulsions. However, substitution group on aromatic ring could have a great impact on π-π interaction by changing electron repulsion force between two rings. To investigate π-π interaction between ligand and aromatic side chain of protein, Brookhaven Protein Data Bank was analyzed. We extracted isolated dimer pairs with the aim of excluding multiple π-π stacking effects and found that T-shaped conformation is prevalent among aromatic interaction between phenyl ring of ligand and protein, which corresponds with the phenomenon of Phe-Phe interactions in small peptide. Specifically, for the non-substitution model, both Phe-Phe and Phenyl-Phe exhibit a favored T-shaped conformation whose dihedral angle is around 50°-70° and centroid distance is between 5.0 and 5.6 Å. However, it could be changed by substituent effect. The hydroxyl group could contact in the case of Tyr-Tyr pairs, while they point away from phenyl plane in Phe-Tyr pairs. PMID:26370211
Weber, Gerald
2013-01-01
Information about molecular interactions in DNA can be obtained from experimental melting temperature data by using mesoscopic statistical physics models. Here, we extend the technique to RNA and show that the new parameters correctly reproduce known properties such as the stronger hydrogen bonds of AU base pairs. We also were able to calculate a complete set of elastic constants for all 10 irreducible combinations of nearest neighbours (NNs). We believe that this is particularly useful as experimentally derived information about RNA elasticity is relatively scarce. The melting temperature prediction using the present model improves over those from traditional NN model, providing thus an alternative way to calculate these temperatures for RNA. Additionally, we calculated the site-dependent base pair oscillation to explain why RNA shows larger oscillation amplitudes despite having stronger AU hydrogen bonds. PMID:23087379
On strongly nonlinear vortex/wave interactions in boundary-layer transition
NASA Technical Reports Server (NTRS)
Hall, Philip; Smith, Frank T.
1989-01-01
The interactions between longitudinal vortices and accompanying waves considered are strongly nonlinear, in the sense that the mean-flow profile throughout the boundary layer is completely altered from its original undisturbed state. Nonlinear interactions between vortex flow and Tollmien-Schlichting waves are addressed first, and some analytical and computational properties are described. These include the possibility in the spatial-development case of a finite-distance break-up, inducing a singularity in the displacement thickness. Second, vortex/Rayleigh wave nonlinear interactions are considered for the compressible boundary-layer, along with certain special cases of interest and some possible solution properties. Both types, vortex/Tollmien-Schlichting and vortex/Rayleigh, are short-scale/long-scale interactions and they have potential applications to many flows at high Reynolds numbers. The strongly nonlinear nature is believed to make them very relevant to fully fledged transition to turbulence.
Nonlinear Interactions between Slender Structures and Axial Flow
NASA Astrophysics Data System (ADS)
Du, Li
2015-03-01
For decades, dynamic behaviors of a slender structure with axial flow have been extensively studied. However, the governing equation based on expansions of small quantities is complicatedly-expressed and can be inappropriate as amplitude becomes considerably large. In this research, we are dedicated to finding an approach to study the nonlinear dynamics of a fluid-conveying slender strcture with arbitrary amplitude. By introducing the Intrinsic Coordinate, we find a concise way to describe the configuration of the system. Differential relations of such coordinate are studied and the rigorous nonlinear equation of motion is derived. Then rather than small-deflection approximation, linear dynamics are studied using Argand Diagram under a weaker condition named low-varying approximation. Nonlinear properties including Hopf bifurcation, limit-cycle motion and vibration frequencies are studied theoretically and experimentally.
NASA Technical Reports Server (NTRS)
Jarrah, Yousef Mohd
1989-01-01
The nonlinear interactions between a fundamental instability mode and both its harmonics and the changing mean flow are studied using the weakly nonlinear stability theory of Stuart and Watson, and numerical solutions of coupled nonlinear partial differential equations. The first part focuses on incompressible cold (or isothermal; constant temperature throughout) mixing layers, and for these, the first and second Landau constants are calculated as functions of wavenumber and Reynolds number. It is found that the dominant contribution to the Landau constants arises from the mean flow changes and not from the higher harmonics. In order to establish the range of validity of the weakly nonlinear theory, the weakly nonlinear and numerical solutions are compared and the limitation of each is discussed. At small amplitudes and at low-to-moderate Reynolds numbers, the two results compare well in describing the saturation of the fundamental, the distortion of the mean flow, and the initial stages of vorticity roll-up. At larger amplitudes, the interaction between the fundamental, second harmonic, and the mean flow is strongly nonlinear and the numerical solution predicts flow oscillations, whereas the weakly nonlinear theory yields saturation. In the second part, the weakly nonlinear theory is extended to heated (or nonisothermal; mean temperature distribution) subsonic round jets where quadratic and cubic nonlinear interactions are present, and the Landau constants also depend on jet temperature ratio, Mach number and azimuthal mode number. Under exponential growth and nonlinear saturation, it is found that heating and compressibility suppress the growth of instability waves, that the first azimuthal mode is the dominant instability mode, and that the weakly nonlinear solution describes the early stages of the roll-up of an axisymmetric shear layer. The receptivity of a typical jet flow to pulse type input disturbance is also studied by solving the initial value problem
NASA Astrophysics Data System (ADS)
Takaoka, Masanori; Yokoyama, Naoto
2015-01-01
The real-space dynamics and the nonlinear interactions among Fourier modes in elastic wave turbulence are investigated by simulating the Foppl-von Karman equation. We find that the bundle structures of ridges appear intermittently in the time evolution of the stretching energy field. The time-evolution of the nonlinearity indicates the existence of active and moderate phases in turbulent state. Conditional sampling analysis reveals that the bundle structure, which is the embodiment of the strong nonlinear interactions among modes, induces the energy supply from an external force to the system.
Beach steepness effects on nonlinear infragravity-wave interactions: A numerical study
NASA Astrophysics Data System (ADS)
de Bakker, A. T. M.; Tissier, M. F. S.; Ruessink, B. G.
2016-01-01
The numerical model SWASH is used to investigate nonlinear energy transfers between waves for a diverse set of beach profiles and wave conditions, with a specific focus on infragravity waves. We use bispectral analysis to study the nonlinear triad interactions, and estimate energy transfers to determine energy flows within the spectra. The energy transfers are divided into four types of triad interactions, with triads including either one, two or three infragravity-frequency components, and triad interactions solely between sea-swell wave frequencies. The SWASH model is validated with a high-resolution laboratory data set on a gently sloping beach, which shows that SWASH is capable of modeling the detailed nonlinear interactions. From the simulations, we observe that especially the beach slope affects nonlinear infragravity-wave interactions. On a low-sloping beach, infragravity-wave energy dominates the water motion close to shore. Here infragravity-infragravity interactions dominate and generate higher harmonics that lead to the steepening of the infragravity wave and eventually breaking, causing large infragravity energy dissipation. On the contrary, on a steep-sloping beach, sea-swell wave energy dominates the water motion everywhere. Here infragravity frequencies interact with the spectral peak and spread energy to a wide range of higher frequencies, with relatively less infragravity energy dissipation. Although both beach types have different nonlinear interaction patterns during infragravity-wave dissipation, the amount of infragravity-wave reflection can be estimated by a single parameter, the normalized bed slope.
NASA Astrophysics Data System (ADS)
Berger, Or; Adler-Abramovich, Lihi; Levy-Sakin, Michal; Grunwald, Assaf; Liebes-Peer, Yael; Bachar, Mor; Buzhansky, Ludmila; Mossou, Estelle; Forsyth, V. Trevor; Schwartz, Tal; Ebenstein, Yuval; Frolow, Felix; Shimon, Linda J. W.; Patolsky, Fernando; Gazit, Ehud
2015-05-01
The two main branches of bionanotechnology involve the self-assembly of either peptides or DNA. Peptide scaffolds offer chemical versatility, architectural flexibility and structural complexity, but they lack the precise base pairing and molecular recognition available with nucleic acid assemblies. Here, inspired by the ability of aromatic dipeptides to form ordered nanostructures with unique physical properties, we explore the assembly of peptide nucleic acids (PNAs), which are short DNA mimics that have an amide backbone. All 16 combinations of the very short di-PNA building blocks were synthesized and assayed for their ability to self-associate. Only three guanine-containing di-PNAs—CG, GC and GG—could form ordered assemblies, as observed by electron microscopy, and these di-PNAs efficiently assembled into discrete architectures within a few minutes. The X-ray crystal structure of the GC di-PNA showed the occurrence of both stacking interactions and Watson-Crick base pairing. The assemblies were also found to exhibit optical properties including voltage-dependent electroluminescence and wide-range excitation-dependent fluorescence in the visible region.
NASA Astrophysics Data System (ADS)
Tagami, Masayoshi; Inoue, Naoya; Ueki, Makoto; Narihiro, Mitsuru; Tada, Munehiro; Yamamoto, Hironori; Ito, Fuminori; Furutake, Naoya; Saito, Shinobu; Onodera, Takahiro; Takeuchi, Tsuneo; Hayashi, Yoshihiro
2012-09-01
Low capacitance and highly reliable Cu dual-damascene (DD) interconnects have been developed with self-organized “seamless low-k SiOCH stacks” (SEALS) structure. A carbon-rich sub-nano porous SiOCH (k=2.5) was directly stacked on an oxygen-rich porous SiOCH (k=2.7) in the SEALS structure, without a hard-mask (HM) and etch-stop (ES) layer of SiO2. The effective k-value (keff) of the Cu DD interconnect including the SiCN capping layer (k=4.9) was reduced to 2.9 compared to 3.4 on a conventional hybrid structure with SiO2-HM and ES, which had been used in 65-nm-node mass production. The interconnect delay of a 45-nm-node complementary metal oxide semiconductor (CMOS) ring oscillator (RO) was reduced by 15% referring to that of the conventional hybrid structure. Interconnect reliabilities, such as the interline time dependent dielectric breakdown (TDDB) and thermal cycles, were unchanged from those of the conventional hybrid interconnects. No failure was detected for chip package interaction (CPI) during reliability tests in a plastic ball grid array (PBGA) package. SEALS is a promising structure for scaled down ultra large scale integrations (ULSIs) for highly reliable and high speed operation, and low power consumption.
On triad nonlinear resonant interactions of deep water waves trapped by jet currents
NASA Astrophysics Data System (ADS)
Shrira, Victor; Slunyaev, Alexey
2014-05-01
We derive an asymptotic description of weakly nonlinear wave interactions between waves trapped by opposing jet currents by extending the asymptotic modal approach developed in Shrira & Slunyaev (2014). It is widely believed that to the leading order the nonlinear interactions between water waves in deep water are always quartic and potential. We show that for waves trapped on the jet currents it is not true: triad resonant interactions between trapped modes are always allowed. Moreover, the nonlinear evolution of the wave field is to the leading order determined by these triad interactions if the current is sufficiently strong or wave field nonlinearity is appropriately weak. To the leading order the corresponding interaction coefficients are controlled by the background vorticity due to the jet. More specifically, we consider waves upon a longitudinally uniform jet current; the current is assumed to be stationary and without vertical shear. The approximate separation of variables allows us to find the two-dimensional mode structure by means of one-dimensional boundary value problem (BVP) for wave Fourier harmonics along the current. The asymptotic weakly nonlinear theory taking into account quadratic nonlinearity for broad but not necessary weak currents is developed. The evolution equations for three interacting modes are written explicitly, the nonlinear interaction coefficients are computed. The three-wave interactions weaken when the current is weak. When the ratio of the current magnitude to wave celerity is of order of wave steepness the effects of 3-wave and 4-wave resonances appear at the same asymptotic order. These regimes, as well as the identified regimes where triad resonant interactions between trapped waves are dominant, lead to a qualitatively new wave dynamics which remains to be explored yet. V.I. Shrira, A.V. Slunyaev, Trapped waves on jet currents: asymptotic modal approach. J. Fluid Mech. 738, 65-104 (2014).
Al-Khateeb, Mohammad A Z; McCarthy, Mary; Sánchez, Christian; Ellis, Andrew
2016-04-15
In this Letter, we theoretically and numerically analyze the performance of coherent optical transmission systems that deploy inline or transceiver based nonlinearity compensation techniques. For systems where signal-signal nonlinear interactions are fully compensated, we find that beyond the performance peak the signal-to-noise ratio degradation has a slope of 3 dB_{SNR}/dB_{Power} suggesting a quartic rather than quadratic dependence on signal power. This is directly related to the fact that signals in a given span will interact not only with linear amplified spontaneous emission noise, but also with the nonlinear four-wave mixing products generated from signal-noise interaction in previous (hitherto) uncompensated spans. The performance of optical systems employing different nonlinearity compensation schemes were numerically simulated and compared against analytical predictions, showing a good agreement within a 0.4 dB margin of error. PMID:27082361
Finite element modeling of nonlinear piezoelectric energy harvesters with magnetic interaction
NASA Astrophysics Data System (ADS)
Upadrashta, Deepesh; Yang, Yaowen
2015-04-01
Piezoelectric energy harvesting from ambient vibrations is a potential technology for powering wireless sensors and low power electronic devices. The conventional linear harvesters suffer from narrow operational bandwidth. Many attempts have been made especially using the magnetic interaction to broaden the bandwidth of harvesters. The finite element (FE) modeling has been used only for analyzing the linear harvesters in the literature. The main difficulties in extending the FE modeling to analyze the nonlinear harvesters involving magnetic interaction are developing the mesh needed for magnetic interaction in dynamic problems and the high demand on computational resource needed for solving the coupled electrical-mechanical-magnetic problem. In this paper, an innovative method is proposed to model the magnetic interaction without inclusion of the magnetic module. The magnetic force is modeled using the nonlinear spring element available in ANSYS finite element analysis (FEA) package, thus simplifying the simulation of nonlinear piezoelectric energy harvesters as an electromechanically coupled problem. Firstly, an FE model of a monostable nonlinear harvester with cantilever configuration is developed and the results are validated with predictions from the theoretical model. Later, the proposed technique of FE modeling is extended to a complex 2-degree of freedom nonlinear energy harvester for which an accurate analytical model is difficult to derive. The performance predictions from FEA are compared with the experimental results. It is concluded that the proposed modeling technique is able to accurately analyze the behavior of nonlinear harvesters with magnetic interaction.
Nonlinear interaction between pulse and noise signals in nondispersive media
NASA Astrophysics Data System (ADS)
Gurbatov, S. N.; Demin, I. Iu.; Pronchatov-Rubtsov, N. V.
1986-10-01
The evolution of a perturbation which initially represents the sum of a regular pulsed signal and stationary noise is investigated by using the nonlinear Burgers equation. The effect of a decrease in the pulse front velocity and its broadening due to turbulent viscosity is identified. An abrupt increase in noise dispersion in the discontinuity region and a decrease in noise dispersion at the trailing edge of a pulse are also noted. Results of a numerical simulation are presented.
The dynamics of interacting nonlinearities governing long wavelength driftwave turbulence
Newman, D.E.
1993-09-01
Because of the ubiquitous nature of turbulence and the vast array of different systems which have turbulent solutions, the study of turbulence is an area of active research. Much present day understanding of turbulence is rooted in the well established properties of homogeneous Navier-Stokes turbulence, which, due to its relative simplicity, allows for approximate analytic solutions. This work examines a group of turbulent systems with marked differences from Navier-Stokes turbulence, and attempts to quantify some of their properties. This group of systems represents a variety of drift wave fluctuations believed to be of fundamental importance in laboratory fusion devices. From extensive simulation of simple local fluid models of long wavelength drift wave turbulence in tokamaks, a reasonably complete picture of the basic properties of spectral transfer and saturation has emerged. These studies indicate that many conventional notions concerning directions of cascades, locality and isotropy of transfer, frequencies of fluctuations, and stationarity of saturation are not valid for moderate to long wavelengths. In particular, spectral energy transfer at long wavelengths is dominated by the E {times} B nonlinearity, which carries energy to short scale in a manner that is highly nonlocal and anisotropic. In marked contrast to the canonical self-similar cascade dynamics of Kolmogorov, energy is efficiently passed between modes separated by the entire spectrum range in a correlation time. At short wavelengths, transfer is dominated by the polarization drift nonlinearity. While the standard dual cascade applies in this subrange, it is found that finite spectrum size can produce cascades that are reverse directed and are nonconservative in enstrophy and energy similarity ranges. In regions where both nonlinearities are important, cross-coupling between the nolinearities gives rise to large no frequency shifts as well as changes in the spectral dynamics.
Nonlinear Dynamics of Bose-Einstein Condensates with Long-Range Interactions
Wunner, G.; Cartarius, H.; Fabcic, T.; Koeberle, P.; Main, J.; Schwidder, T.
2008-11-13
The motto of this paper is: Let's face Bose-Einstein condensation through nonlinear dynamics. We do this by choosing variational forms of the condensate wave functions (of given symmetry classes), which convert the Bose-Einstein condensates via the time-dependent Gross-Pitaevskii equation into Hamiltonian systems that can be studied using the methods of nonlinear dynamics. We consider in particular cold quantum gases where long-range interactions between the neutral atoms are present, in addition to the conventional short-range contact interaction, viz. gravity-like interactions, and dipole-dipole interactions. The results obtained serve as a useful guide in the search for nonlinear dynamics effects in numerically exact quantum calculations for Bose-Einstein condensates. A main result is the prediction of the existence of stable islands as well as chaotic regions for excited states of dipolar condensates, which could be checked experimentally.
Nonlinear interaction of drift waves with driven plasma currents
Brandt, Christian; Grulke, Olaf; Klinger, Thomas
2010-03-15
In a cylindrical magnetized plasma, coherent drift wave modes are synchronized by a mode selective drive of plasma currents. Nonlinear effects of the synchronization are investigated in detail. Frequency pulling is observed over a certain frequency range. The dependence of the width of this synchronization range on the amplitude of the driven plasma currents forms Arnold tongues. The transition between complete and incomplete synchronization is indicated by the onset of periodic pulling and phase slippage. Synchronization is observed for driven current amplitudes, which are some percent of the typical value of parallel currents generated by drift waves.
Nonlinear interaction between wave and convective disturbances in the solar corona
NASA Astrophysics Data System (ADS)
Veselovsky, I. S.; Mikhalyaev, B. B.; Bembitov, D. B.
2015-12-01
During more than two decades, many non-stationary events have been observed in the solar corona by different ground and space instruments, namely: oscillations and flows. These events play a crucial role in a solving two important problems of the solar physics: coronal heating and solar wind acceleration. Numerous observational data and theoretical works demonstrate the nonlinear interaction between waves and flows in the solar atmosphere. On other hand, nonlinear effects can also be used in coronal seismology, where a significant success leaded to many original works on linear disturbances in the coronal plasma. The nonlinear approach should make it possible to achieve more precise results.
Petrov, Georgi I.; Zhi, Miaochan; Yakovlev, Vladislav V.
2013-01-01
We experimentally investigated the nonlinear optical interaction between the instantaneous four-wave mixing and the cascaded quadratic frequency conversion in commonly used nonlinear optical KTP and LiNbO3 with the aim of a possible background suppression of the non-resonant background in coherent anti-Stokes Raman scattering. The possibility of background-free heterodyne coherent anti-Stokes Raman scattering microspectroscopy is investigated at the interface formed by a liquid (isopropyl alcohol) and a nonlinear crystal (LiNbO3). PMID:24514791
Gresh, Nohad; Sponer, Judit E; Devereux, Mike; Gkionis, Konstantinos; de Courcy, Benoit; Piquemal, Jean-Philip; Sponer, Jiri
2015-07-30
Until now, atomistic simulations of DNA and RNA and their complexes have been executed using well calibrated but conceptually simple pair-additive empirical potentials (force fields). Although such simulations provided many valuable results, it is well established that simple force fields also introduce errors into the description, underlying the need for development of alternative anisotropic, polarizable molecular mechanics (APMM) potentials. One of the most abundant forces in all kinds of nucleic acids topologies is base stacking. Intra- and interstrand stacking is assumed to be the most essential factor affecting local conformational variations of B-DNA. However, stacking also contributes to formation of all kinds of noncanonical nucleic acids structures, such as quadruplexes or folded RNAs. The present study focuses on 14 stacked cytosine (Cyt) dimers and the doubly H-bonded dimer. We evaluate the extent to which an APMM procedure, SIBFA, could account quantitatively for the results of high-level quantum chemistry (QC) on the total interaction energies, and the individual energy contributions and their nonisotropic behaviors. Good agreements are found at both uncorrelated HF and correlated DFT and CCSD(T) levels. Resorting in SIBFA to distributed QC multipoles and to an explicit representation of the lone pairs is essential to respectively account for the anisotropies of the Coulomb and of the exchange-repulsion QC contributions. PMID:26119247
Nonlinear Optical Interactions in Bacteriorhodopsin Using Z-Scan
NASA Astrophysics Data System (ADS)
Aranda, Francisco J.; Rao, Devulapalli V. G. L. N.; Wong, Chi L.; Zhou, Ping; Chen, Zhong; Akkara, Joseph A.; Kaplan, David L.; Roach, Joseph F.
1995-06-01
Nonlinear refractive index coefficient n2 of bacteriorhodopsin suspensions in water is measured by the Z-scan technique with a low power continuous wave laser at 647.1 manometer wavelength. Our results indicate that both the magnitude and the sign of n2 depend strongly on the light intensity. Negative values for n2 are obtained for on axis laser irradiance at the focus above 3 W/cm2. The observed self-defocusing phenomena can be attributed to the index change due to the light induced transition between the photochromic states. The results elucidate the origin of n2 and offer a plausible explanation for the differences in the reported n2 measurements.
Interaction dynamics in small networks of nonlinear elements
NASA Astrophysics Data System (ADS)
Stich, Michael; Velarde, Manuel G.
2015-03-01
We study a small circuit of coupled nonlinear elements to investigate general features of signal transmission through networks. The small circuit itself is perceived as building block for larger networks. Individual dynamics and coupling are motivated by neuronal systems: We consider two types of dynamical modes for an individual element, regular spiking and chattering and each individual element can receive excitatory and/or inhibitory inputs and is subjected to different feedback types (excitatory and inhibitory; forward and recurrent). Both, deterministic and stochastic simulations are carried out to study the input-output relationships of these networks. Major results for regular spiking elements include frequency locking, spike rate amplification for strong synaptic coupling, and inhibition-induced spike rate control which can be interpreted as a output frequency rectification. For chattering elements, spike rate amplification for low frequencies and silencing for large frequencies is characteristic.
Chaotic saddles in nonlinear modulational interactions in a plasma
Miranda, Rodrigo A.; Rempel, Erico L.; Chian, Abraham C.-L.
2012-11-15
A nonlinear model of modulational processes in the subsonic regime involving a linearly unstable wave and two linearly damped waves with different damping rates in a plasma is studied numerically. We compute the maximum Lyapunov exponent as a function of the damping rates in a two-parameter space, and identify shrimp-shaped self-similar structures in the parameter space. By varying the damping rate of the low-frequency wave, we construct bifurcation diagrams and focus on a saddle-node bifurcation and an interior crisis associated with a periodic window. We detect chaotic saddles and their stable and unstable manifolds, and demonstrate how the connection between two chaotic saddles via coupling unstable periodic orbits can result in a crisis-induced intermittency. The relevance of this work for the understanding of modulational processes observed in plasmas and fluids is discussed.
NASA Astrophysics Data System (ADS)
Korchemskaya, Elena Y.; Soskin, Marat S.; Stepanchikov, Dmitriy A.; Druzhko, Anna B.; Dyukova, Tatyana V.
1996-06-01
The effect of protein and matrix modifications on the photoanisotropic properties is studied for developing the concept of impact upon the main optical properties of the dynamic optical material based on bacteriorhodopsin (BR) both interaction of transmembrane protein--chromophore complex BR with matrix and interaction of protein opsin with chromophore retinal. Also possibility of the application of BR-films for the light polarization modulator is proposed.
NASA Astrophysics Data System (ADS)
Zhao, Wen-Lei; Ding, Cai-Ying; Liu, Jie; Fu, Li-Bin
2016-06-01
We investigate the quantum transport dynamics of periodically delta-kicked Bose–Einstein condensate under the effect of spatially modulated nonlinear interactions. The spatial modulation frequency can dramatically affect the transport behaviors of the ultra-cold atoms. For odd frequency, the linear growth of the directed current is close to that of the noninteracting case for not very strong nonlinear interaction. Both the acceleration and the quantum state evolution gradually approach that of the noninteracting case with increasing frequency. For other values of frequency, a very weak nonlinear interaction can dramatically reduce the linear growth of the directed current. The quantum state evolution differs rapidly from that of the noninteracting case. The underlying dynamic mechanism is uncovered and some important implications are addressed.
Schwartz, Sylvain; Feugnet, Gilles; Pocholle, Jean-Paul; Gutty, Francois; Bouyer, Philippe
2008-05-09
We report fine-tuning of nonlinear interactions in a solid-state ring laser gyroscope by vibrating the gain medium along the cavity axis. We demonstrate both experimentally and theoretically that nonlinear interactions vanish for some values of the vibration parameters, leading to quasi-ideal rotation sensing. We eventually point out that our conclusions can be mapped onto other subfields of physics such as ring-shaped superfluid configurations, where nonlinear interactions could be tuned by using Feshbach resonance.
Topological charge algebra of optical vortices in nonlinear interactions.
Zhdanova, Alexandra A; Shutova, Mariia; Bahari, Aysan; Zhi, Miaochan; Sokolov, Alexei V
2015-12-28
We investigate the transfer of orbital angular momentum among multiple beams involved in a coherent Raman interaction. We use a liquid crystal light modulator to shape pump and Stokes beams into optical vortices with various integer values of topological charge, and cross them in a Raman-active crystal to produce multiple Stokes and anti-Stokes sidebands. We measure the resultant vortex charges using a tilted-lens technique. We verify that in every case the generated beams' topological charges obey a simple relationship, resulting from angular momentum conservation for created and annihilated photons, or equivalently, from phase-matching considerations for multiple interacting beams. PMID:26832066
ERIC Educational Resources Information Center
Naylor, Jim
2005-01-01
Chimneys and stacks appear to be strong and indestructible, but chimneys begin to deteriorate from the moment they are built. Early on, no signs are apparent; but deterioration accelerates in subsequent years, and major repairs are soon needed instead of minor maintenance. With proper attention, most structures can be repaired and continue to…
Simulations of energetic particles interacting with nonlinear anisotropic dynamical turbulence
NASA Astrophysics Data System (ADS)
Heusen, M.; Shalchi, A.
2016-09-01
We investigate test-particle diffusion in dynamical turbulence based on a numerical approach presented before. For the turbulence we employ the nonlinear anisotropic dynamical turbulence model which takes into account wave propagation effects as well as damping effects. We compute numerically diffusion coefficients of energetic particles along and across the mean magnetic field. We focus on turbulence and particle parameters which should be relevant for the solar system and compare our findings with different interplanetary observations. We vary different parameters such as the dissipation range spectral index, the ratio of the turbulence bendover scales, and the magnetic field strength in order to explore the relevance of the different parameters. We show that the bendover scales as well as the magnetic field ratio have a strong influence on diffusion coefficients whereas the influence of the dissipation range spectral index is weak. The best agreement with solar wind observations can be found for equal bendover scales and a magnetic field ratio of δ B / B0 = 0.75.
Nonlinear geosphere-biosphere interactions and the Cambrian explosion
NASA Astrophysics Data System (ADS)
von Bloh, W.; Bounama, C.; Franck, S.
2003-04-01
A conceptual model for the global carbon cycle of the Earth containing the reservoirs mantle, ocean floor, continental crust, continental biosphere, the kerogen , as well as the aggregated reservoir ocean and atmosphere is presented. In this study the evolution of the mean global surface temperature, the biomass, and reservoir sizes over the whole history and future of the Earth under a maturing Sun is investigated. Reasonable values for the present distribution of carbon in the surface reservoirs of the Earth are obtained and a pronounced global minimum of mean surface temperature at the present state of the Earth is found. Furthermore, three different biosphere types are introduced: procaryotes, eucaryotes, and higher metazoa. They all differ in their temperature tolerance interval and their biogenic enhancement of silicate rock weathering. Around 500 Myr in the past we find a rise of higher metazoa caused by the nonlinear feedback between biosphere and climate. Biotic amplifying of weathering provides and maintains the environment of higher life forms. Such a mechanism may explain the so-called Cambrian explosion.
Nonlinear Scale Interactions and Energy Pathways in the Ocean
NASA Astrophysics Data System (ADS)
Aluie, Hussein; Hecht, Matthew; Vallis, Geoffrey; Bryan, Kirk; Maltrud, Mathew; Ecke, Robert; Wingate, Beth
2013-03-01
Large-scale currents and eddies pervade the ocean and play a prime role in the general circulation and climate. The coupling between scales ranging from O (104) km down to O (1) mm presents a major difficulty in understanding, modeling, and predicting oceanic circulation and mixing, where the energy budget is uncertain within a factor possibly as large as ten. Identifying the energy sources and sinks at various scales can reduce such uncertainty and yield insight into new parameterizations. To this end, we refine a novel coarse-graining framework to directly analyze the coupling between scales. The approach is very general, allows for probing the dynamics simultaneously in scale and in space, and is not restricted by usual assumptions of homogeneity or isotropy. We apply these tools to study the energy pathways from high-resolution ocean simulations using LANL's Parallel Ocean Program. We examine the extent to which the traditional paradigm for such pathways is valid at various locations such as in western boundary currents, near the equator, and in the deep ocean. We investigate the contribution of various nonlinear mechanisms to the transfer of energy across scales such as baroclinic and barotropic instabilities, barotropization, and Rossby wave generation.
Nonlinear Scale Interactions and Energy Pathways in the Ocean
NASA Astrophysics Data System (ADS)
Aluie, Hussein; Hecht, Matthew; Vallis, Geoffrey
2013-11-01
Large-scale currents and eddies pervade the ocean and play a prime role in the general circulation and climate. The coupling between scales ranging from O (104) km down to O (1) mm presents a major difficulty in understanding, modeling, and predicting oceanic circulation and mixing, where the energy budget is uncertain within a factor possibly as large as ten. Identifying the energy sources and sinks at various scales can reduce such uncertainty and yield insight into new parameterizations. To this end, we refine a novel coarse-graining framework to directly analyze the coupling between scales. The approach is very general, allows for probing the dynamics simultaneously in scale and in space, and is not restricted by usual assumptions of homogeneity or isotropy. We apply these tools to study the energy pathways from high-resolution ocean simulations using LANL's Parallel Ocean Program. We examine the extent to which the traditional paradigm for such pathways is valid at various locations such as in western boundary currents, near the equator, and in the deep ocean. We investigate the contribution of various nonlinear mechanisms to the transfer of energy across scales such as baroclinic and barotropic instabilities.
Mikhalyova, Elena A; Yakovenko, Anastasiya V; Zeller, Matthias; Kiskin, Mikhail A; Kolomzarov, Yuriy V; Eremenko, Igor L; Addison, Anthony W; Pavlishchuk, Vitaly V
2015-04-01
The three new complexes Tp(Py)Ln(CH3CO2)2(H2O) (Ln = Eu (1), Gd(2), or Tb (3)) were prepared and characterized crystallographically. In the crystal lattices of these complexes, separate molecules are connected in infinite chains by π-stacking interactions. Complexes 1 and 3 display intense photoluminescence and triboluminescence (red and green respectively), while compound 3 exhibits electroluminescence commencing at 9 V in an ITO/PVK/3/Al device (ITO = indium-tin oxide, PVK = poly(N-vinylcarbazole)). A series of Eu/Tb-doped Gd compounds was prepared by cocrystallization from mixtures of 1 and 2 or 2 and 3, respectively. It was shown that π-stacking interactions are involved in increasing the efficiency of energy transfer from the gadolinium complex to emitting [Tp(Py)Eu](2+) or [Tp(Py)Tb](2+) centers, and this energy transfer occurs through hundreds of molecules, resembling the process of energy harvesting in chloroplast stacks. PMID:25797500
Nonlinear interaction of fast particles with Alfven waves in toroidal plasmas
Candy, J.; Borba, D.; Huysmans, G.T.A.; Kerner, W.; Berk, H.L.
1996-12-17
A numerical algorithm to study the nonlinear, resonant interaction of fast particles with Alfven waves in tokamak geometry has been developed. The scope of the formalism is wide enough to describe the nonlinear evolution of fishbone modes, toroidicity-induced Alfven eigenmodes and ellipticity-induced Alfven eigenmodes, driven by both passing and trapped fast ions. When the instability is sufficiently weak, it is known that the wave-particle trapping nonlinearity will lead to mode saturation before wave-wave nonlinearities are appreciable. The spectrum of linear modes can thus be calculated using a magnetohydrodynamic normal-mode code, then nonlinearly evolved in time in an efficient way according to a two-time-scale Lagrangian dynamical wave model. The fast particle kinetic equation, including the effect of orbit nonlinearity arising from the mode perturbation, is simultaneously solved of the deviation, {delta}f = f {minus} f{sub 0}, from an initial analytic distribution f{sub 0}. High statistical resolution allows linear growth rates, frequency shifts, resonance broadening effects, and nonlinear saturation to be calculated quickly and precisely. The results have been applied to an ITER instability scenario. Results show that weakly-damped core-localized modes alone cause negligible alpha transport in ITER-like plasmas--even with growth rates one order of magnitude higher than expected values. However, the possibility of significant transport in reactor-type plasmas due to weakly unstable global modes remains an open question.
NASA Astrophysics Data System (ADS)
Katoh, Y.; Kitahara, M.; Kojima, H.; Omura, Y.; Kasahara, S.; Hirahara, M.; Miyoshi, Y.; Seki, K.; Asamura, K.; Takashima, T.
2012-12-01
We study the statistical significance of the Wave Particle Interaction Analyzer (WPIA) for measurement of the energy transfer process between energetic electrons and whistler-mode chorus emissions in the Earth's inner magnetosphere. The WPIA measures a relative phase angle between the wave vector and velocity vector of each particle and computes an inner product W(t), while W(t) is equivalent to the variation of the kinetic energy of energetic electrons interacting with plasma waves. The WPIA measurements will be realized by the Software-type WPIA in the SPRINT-B/ERG satellite mission. In the present study, we evaluate the feasibility of WPIA by applying the WPIA analysis to the simulation results on whistler-mode chorus generation. We compute W(t) of a wave electric field observed at a fixed point assumed in the simulation system and a velocity vector of each energetic electron passing through the assumed point. By integrating W(t) in time, we obtain significant values of W_{int} in the kinetic energy and pitch angle ranges as expected from the evolution of chorus emissions in the simulation result. The statistical significance of the obtained W_{int} is evaluated by calculating the standard deviation σ_W of W_{int}. We show that W_{int} greater than σ_W is obtained in the velocity phase space corresponding to the wave generation and acceleration of relativistic electrons. We conduct another analysis of a distribution of energetic electrons in the wave phase space using the same dataset of the simulation results. We clarify that the deviation of the distribution in the wave phase space is found in the velocity phase space corresponding to the large W_{int} values, which is consistent with formation of nonlinear resonant currents assumed in the generation mechanism of chorus emissions. The present study suggests that the statistical significance of the WPIA can be evaluated by calculating σ_W of W_{int}, and reveals the feasibility of the WPIA, which will be on
Gunaydin, Hakan; Bartberger, Michael D
2016-04-14
This viewpoint describes the results obtained from matched molecular pair analyses and quantum mechanics calculations that show unsaturated rings found in drug-like molecules may be replaced with their saturated counterparts without losing potency even if they are engaged in stacking interactions with the side chains of aromatic residues. PMID:27096037
On the dispersion relation of nonlinear wave current interaction by means of the HAM
NASA Astrophysics Data System (ADS)
Liu, Zeng; Lin, Zhiliang; Liao, Shijun
2012-09-01
The influence of exponentially sheared currents on unidirectional bichromatic waves in deep water is investigated by the HAM. The governing equations contain four coupled PDEs, including a nonlinear vorticity transport equation and two nonlinear free-surface conditions on the unknown wave elevation. No constrain is made for the primary wave amplitudes, and the current owns a exponential type profile along the vertical line. Convergent solutions are obtained with the help of convergence-control parameter. It is found that a critical characteristic current profile slope exists for each parts of phase velocity caused by nonlinear interaction, under/above which the mean flow vorticity increases/decreases the corresponding part of phase velocity. This work indicates that the HAM is a powerful tool for complicated coupled nonlinear PDEs, which deserves more attention for further development.
Nonlinear modes of an intense laser beam interacting with a periodic lattice of nanoparticle
Sepehri Javan, N. Homami, S. H. H.
2015-08-15
Self-guided nonlinear propagation of an intense laser beam through a periodic lattice of nanoparticle is studied. Using a perturbative method, a cubic nonlinear wave equation describing the laser-nanoparticle interaction in the weakly relativistic regime is derived. Transverse Eigen modes of the laser, nonlinear dispersion relation and its related group velocity are obtained. It is shown that the best fitted function to the transverse profile is Gaussian. Effect of the laser amplitude and also the ratio of nanoparticles radius to their separation on the nonlinear dispersion and amplitude profiles are investigated. It is found that the increase in the just mentioned parameters leads to the localization of transverse profile around the propagation axis.
Mikulski, Damian; Molski, Marcin
2012-07-01
Accurate quantum-chemical calculations based on the second-order Møller-Plesset perturbation method (MP2) and density functional theory (DFT) were performed for the first time to investigate the electronic structures of trans-resveratrol and trans-piceatannol, as well as to study the stacking interaction between trans-resveratrol molecules. Ab initio MP2 calculations performed with using standard split-valence Pople basis sets led us to conclude that these compounds have structures that deviate strongly from planarity, whereas the DFT computations for the same basis sets revealed that the equilibrium geometries of these bioactive polyphenols are planar. Furthermore, the results obtained at the MP2(full)/aug-cc-pVTZ and B3LYP/aug-cc-pVTZ levels indicated that the geometries of trans-resveratrol and trans-piceatannol are practically planar at their absolute energy minima. The relative energies of the equilibrium geometries of trans-resveratrol on its potential energy surface were computed at the MP2(full)/aug-cc-pVTZ level. According to the results obtained, a T-shaped (edge-to-phase) conformer of trans-resveratrol dimer is the most stable in vacuum. This T-shaped conformer is mainly stabilized by strong hydrogen bonding and weak C-H...π interactions. Stacked structures with parallel-displaced trans-stilbene skeletons were also found to be energetically stable. The vertical separation and twist angle dependencies of the stacking energy were investigated at the MP2(full)/aug-cc-pVTZ, B3LYP/aug-cc-pVTZ, and HF/aug-cc-pVTZ levels. The standard B3LYP functional and the Hartree-Fock method neglect long-range attractive dispersion interactions. The MP2 computations revealed that the London dispersion energy cannot be neglected at long or short distances. The stacked model considered here may be useful for predicting the quantum nature of the interactions in π-stacked systems of other naturally occurring stilbenoids, and can help to enhance our understanding of the
Dromion interactions of (2+1)-dimensional nonlinear evolution equations
Ruan; Chen
2000-10-01
Starting from two line solitons, the solution of integrable (2+1)-dimensional mKdV system and KdV system in bilinear form yields a dromion solution or a "Solitoff" solution. Such a dromion solution is localized in all directions and the Solitoff solution decays exponentially in all directions except a preferred one for the physical field or a suitable potential. The interactions between two dromions and between the dromion and Solitoff are studied by the method of figure analysis for a (2+1)-dimensional modified KdV equation and a (2+1)-dimensional KdV type equation. Our analysis shows that the interactions between two dromions may be elastic or inelastic for different forms of solutions. PMID:11089133
Nonlinear interactions that could explain distortion product interference response areas.
Fahey, P F; Stagner, B B; Lonsbury-Martin, B L; Martin, G K
2000-10-01
Suppression and/or enhancement of third- and fifth-order distortion products by a third tone that can have a frequency more than an octave above and a level more than 40 dB below the primary tones have recently been measured by Martin et al. [Hear. Res. 136, 105-123 (1999)]. Contours of iso-suppression and iso-enhancement that are plotted as a function of third-tone frequency and level are called interference response areas. After ruling out order aliasing, two possible mechanisms for this effect have been developed, a harmonic mechanism and a catalyst mechanism. The harmonic mechanism produces distortion products by mixing a harmonic of one of the primary tones with the other primary tone. The catalyst mechanism produces distortion products by mixing one or more intermediate distortion products that are produced by the third tone with one or more of the input tones. The harmonic mechanism does not need a third tone and the catalyst mechanism does. Because the basilar membrane frequency response is predicted to affect each of these mechanisms differently, it is concluded that the catalyst mechanism will be dominant in the high-frequency regions of the cochlea and the harmonic mechanism will have significant strength in the low-frequency regions of the cochlea. The mechanisms are dependent on the existence of both even- and odd-order distortion, and significant even- and odd-order distortion have been measured in the experimental animals. Furthermore, the nonlinear part of the cochlear mechanical response must be well into saturation when input tones are 50 or more dB SPL. PMID:11051505
NASA Astrophysics Data System (ADS)
Okamoto, Kentaro; Tanaka, Toshiyuki; Fujita, Wataru; Awaga, Kunio; Inabe, Tamotsu
2007-08-01
We here examine the electrical and magnetic properties of the isostructural NT3•MCl4 ( NT=naphtho [2,1- d :6,5- d' ]bis([1,2,3] dithiazole and M=Ga and Fe). The crystal structure of NT3•MCl4 consists of one-dimensional π -stacking chains of NT with strong interchain interactions caused by electrostatic Sδ+•••Nδ- contacts. This structure includes four NT molecules with significant differences in molecular structure and charge, exhibiting a characteristic charge ordering, namely, three-dimensional alternation of charge-rich (or -intermediate) and -poor molecules. NT3•GaCl4 and NT3•FeCl4 are found to be semiconductors with σRT˜0.5Scm-1 and to exhibit a nonlinear electrical transport at room temperature with a very low threshold field of 80Vcm-1 for the negative differential resistance. This threshold field significantly increases with a decrease in temperature. The X -band electron paramagnetic resonance (EPR) spectra of NT3•GaCl4 consist of a single-line absorption ascribable to that of the NT+ cation. When the sample is exposed to a current at room temperature, this signal exhibits a drastic decrease in intensity with little change in linewidth. This is attributed to the inhomogeneous formation of EPR-silent conducting pathways for the nonlinear transport. The temperature dependence of the EPR spin susceptibility χs of NT3•GaCl4 suggests a transition toward a spin-gap state below 20K ; χs exhibits a Bonner-Fisher-type temperature dependence above 20K , but gradually collapses to zero below this temperature.
NASA Astrophysics Data System (ADS)
Farokhi, Hamed; Ghayesh, Mergen H.
2016-06-01
This paper analyses the modal interactions in the nonlinear, size-dependent dynamics of geometrically imperfect microplates. Based on the modified couple stress theory, the equations of motion for the in-plane and out-of-plane motions are obtained employing the von Kármán plate theory as well as Kirchhoff's hypotheses by means of the Lagrange equations. The equations of motions are solved using the pseudo-arclength continuation technique and direct time-integration method. The system parameters are tuned to the values associated with modal interactions, and then nonlinear resonant responses and energy transfer are analysed. Nonlinear motion characteristics are shown in the form of frequency-response and force-response curves, time histories, phase-plane portraits, and fast Fourier transforms.
NASA Astrophysics Data System (ADS)
Farokhi, Hamed; Ghayesh, Mergen H.
2015-12-01
This paper analyses the modal interactions in the nonlinear, size-dependent dynamics of geometrically imperfect microplates. Based on the modified couple stress theory, the equations of motion for the in-plane and out-of-plane motions are obtained employing the von Kármán plate theory as well as Kirchhoff's hypotheses by means of the Lagrange equations. The equations of motions are solved using the pseudo-arclength continuation technique and direct time-integration method. The system parameters are tuned to the values associated with modal interactions, and then nonlinear resonant responses and energy transfer are analysed. Nonlinear motion characteristics are shown in the form of frequency-response and force-response curves, time histories, phase-plane portraits, and fast Fourier transforms.
Shukla, P K; Eliasson, B
2007-08-31
We consider nonlinear interactions between intense circularly polarized electromagnetic (CPEM) waves and electron plasma oscillations (EPOs) in a dense quantum plasma, taking into account the electron density response in the presence of the relativistic ponderomotive force and mass increase in the CPEM wave fields. The dynamics of the CPEM waves and EPOs is governed by the two coupled nonlinear Schrödinger equations and Poisson's equation. The nonlinear equations admit the modulational instability of an intense CPEM pump wave against EPOs, leading to the formation and trapping of localized CPEM wave pipes in the electron density hole that is associated with a positive potential distribution in our dense plasma. The relevance of our investigation to the next generation intense laser-solid density plasma interaction experiments is discussed. PMID:17931024
Shukla, P. K.; Eliasson, B.
2007-08-31
We consider nonlinear interactions between intense circularly polarized electromagnetic (CPEM) waves and electron plasma oscillations (EPOs) in a dense quantum plasma, taking into account the electron density response in the presence of the relativistic ponderomotive force and mass increase in the CPEM wave fields. The dynamics of the CPEM waves and EPOs is governed by the two coupled nonlinear Schroedinger equations and Poisson's equation. The nonlinear equations admit the modulational instability of an intense CPEM pump wave against EPOs, leading to the formation and trapping of localized CPEM wave pipes in the electron density hole that is associated with a positive potential distribution in our dense plasma. The relevance of our investigation to the next generation intense laser-solid density plasma interaction experiments is discussed.
A weakly nonlinear theory for wave-vortex interactions in curved channel flow
NASA Technical Reports Server (NTRS)
Singer, Bart A.; Erlebacher, Gordon; Zang, Thomas A.
1992-01-01
A weakly nonlinear theory is developed to study the interaction of Tollmien-Schlichting (TS) waves and Dean vortices in curved channel flow. The predictions obtained from the theory agree well with results obtained from direct numerical simulations of curved channel flow, especially for low amplitude disturbances. Some discrepancies in the results of a previous theory with direct numerical simulations are resolved.
NASA Astrophysics Data System (ADS)
Blackstock, David T.
1987-07-01
Research on four topics in nonlinear acoustics is described. (1) Dependence of three coefficients of nonlinearity for sea water on pressure, temperature, and density. Computation of the coefficients from a combination of theoretical and empirical relations is in progress. (2) Nonlinear, noncollinear interaction of sound waves. Three journal articles have been written, two on interaction in a rectangular waveguide and one on coefficient of nonlinearity for collinear and noncollinear interaction. (3) Reflection and refraction of finite amplitude sound at a plane interface between two fluids. A new form of Snell's law valid for waves of finite amplitude is derived. An experiment to test the implications of the new law is being carried out. (4) Scattering of sound by sound. The classical problem of the secondary radiation produced by interaction of two crossed sound beams is discussed. An experimental test of recent theoretical treatments is in preparation. A preliminary experiment is the measurement of the range dependence of finger lobes in the second harmonic radiation produced in the field of a monochromatically driven piston.
ERIC Educational Resources Information Center
Kelava, Augustin; Werner, Christina S.; Schermelleh-Engel, Karin; Moosbrugger, Helfried; Zapf, Dieter; Ma, Yue; Cham, Heining; Aiken, Leona S.; West, Stephen G.
2011-01-01
Interaction and quadratic effects in latent variable models have to date only rarely been tested in practice. Traditional product indicator approaches need to create product indicators (e.g., x[superscript 2] [subscript 1], x[subscript 1]x[subscript 4]) to serve as indicators of each nonlinear latent construct. These approaches require the use of…
Uranium(IV) Interaction with Aqueous/Solid Interfaces Studied by Nonlinear Optics
Geiger, Franz
2015-03-27
This is the Final Technical Report for "Uranium(IV) Interaction with Aqueous/Solid Interfaces Studied by Nonlinear Optics", by Franz M. Geiger, PI, from Northwestern University, IL, USA, Grant Number SC0004101 and/or DE-PS02-ER09-07.
Nonlinear Interactions within the D-Region Ionosphere
NASA Astrophysics Data System (ADS)
Moore, Robert
2016-07-01
This paper highlights the best results obtained during D-region modification experiments performed by the University of Florida at the High-frequency Active Auroral Research Program (HAARP) observatory between 2007 and 2014. Over this period, we saw a tremendous improvement in ELF/VLF wave generation efficiency. We identified methods to characterize ambient and modified ionospheric properties and to discern and quantify specific types of interactions. We have demonstrated several important implications of HF cross-modulation effects, including "Doppler Spoofing" on HF radio waves. Throughout this talk, observations are compared with the predictions of an ionospheric HF heating model to provide context and guidance for future D-region modification experiments.
Nonlinear interactions and their scaling in the logarithmic region of turbulent channels
NASA Astrophysics Data System (ADS)
Moarref, Rashad; Sharma, Ati S.; Tropp, Joel A.; McKeon, Beverley J.
2014-11-01
The nonlinear interactions in wall turbulence redistribute the turbulent kinetic energy across different scales and different wall-normal locations. To better understand these interactions in the logarithmic region of turbulent channels, we decompose the velocity into a weighted sum of resolvent modes (McKeon & Sharma, J. Fluid Mech., 2010). The resolvent modes represent the linear amplification mechanisms in the Navier-Stokes equations (NSE) and the weights represent the scaling influence of the nonlinearity. An explicit equation for the unknown weights is obtained by projecting the NSE onto the known resolvent modes (McKeon et al., Phys. Fluids, 2013). The weights of triad modes -the modes that directly interact via the quadratic nonlinearity in the NSE- are coupled via interaction coefficients that depend solely on the resolvent modes. We use the hierarchies of self-similar modes in the logarithmic region (Moarref et al., J. Fluid Mech., 2013) to extend the notion of triad modes to triad hierarchies. It is shown that the interaction coefficients for the triad modes that belong to a triad hierarchy follow an exponential function. These scalings can be used to better understand the interaction of flow structures in the logarithmic region and develop analytical results therein. The support of Air Force Office of Scientific Research under Grants FA 9550-09-1-0701 (P.M. Rengasamy Ponnappan) and FA 9550-12-1-0469 (P.M. Doug Smith) is gratefully acknowledged.
Effect of nonlinear soil-structure interaction on seismic response of low-rise SMRF buildings
NASA Astrophysics Data System (ADS)
Raychowdhury, Prishati; Singh, Poonam
2012-12-01
The nonlinear behavior of a soil-foundation system may alter the seismic response of a structure by providing additional fl exibility to the system and dissipating hysteretic energy at the soil-foundation interface. However, the current design practice is still reluctant to consider the nonlinearity of the soil-foundation system, primarily due to lack of reliable modeling techniques. This study is motivated towards evaluating the effect of nonlinear soil-structure interaction (SSI) on the seismic responses of low-rise steel moment resisting frame (SMRF) structures. In order to achieve this, a Winklerbased approach is adopted, where the soil beneath the foundation is assumed to be a system of closely-spaced, independent, nonlinear spring elements. Static pushover analysis and nonlinear dynamic analyses are performed on a 3-story SMRF building and the performance of the structure is evaluated through a variety of force and displacement demand parameters. It is observed that incorporation of nonlinear SSI leads to an increase in story displacement demand and a significant reduction in base moment, base shear and inter-story drift demands, indicating the importance of its consideration towards achieving an economic, yet safe seismic design.
NASA Astrophysics Data System (ADS)
Nunn, David; Omura, Yoshiharu
2015-04-01
Most previous work on nonlinear wave-particle interactions between energetic electrons and VLF waves in the Earth's magnetosphere has assumed parallel propagation, the underlying mechanism being nonlinear trapping of cyclotron resonant electrons in a parabolic magnetic field inhomogeneity. Here nonlinear wave-particle interaction in oblique whistlers in the Earth's magnetosphere is investigated. The study is nonself-consistent and assumes an arbitrarily chosen wave field. We employ a "continuous wave" wave field with constant frequency and amplitude, and a model for an individual VLF chorus element. We derive the equations of motion and trapping conditions in oblique whistlers. The resonant particle distribution function, resonant current, and nonlinear growth rate are computed as functions of position and time. For all resonances of order n, resonant electrons obey the trapping equation, and provided the wave amplitude is big enough for the prevailing obliquity, nonlinearity manifests itself by a "hole" or "hill" in distribution function, depending on the zero-order distribution function and on position. A key finding is that the n = 1 resonance is relatively unaffected by moderate obliquity up to 25°, but growth rates roll off rapidly at high obliquity. The n = 1 resonance saturates due to the adiabatic effect and here reaches a maximum growth at ~20 pT, 2000 km from the equator. Damping due to the n = 0 resonance is not subject to adiabatic effects and maximizes at some 8000 km from the equator at an obliquity ~55°.
Resonant triad in boundary-layer stability. Part 1: Fully nonlinear interaction
NASA Technical Reports Server (NTRS)
Mankbadi, Reda R.
1991-01-01
A first principles theory is developed to study the nonlinear spatial evolution of a near-resonance triad of instability waves in boundary layer transition. This triad consists of a plane wave at fundamental frequency and a pair of symmetrical, oblique waves at the subharmonic frequency. A low frequency, high Reynolds number asymptotic scaling leads to a distinct critical layer where nonlinearity first becomes important; the development of the triad's waves is determined by the critical layer's nonlinear, viscous dynamics. The resulting theory is fully nonlinear in that all nonlinearly generated oscillatory and nonoscillatory components are accounted for. The presence of the plane wave initially causes exponential of exponential growth of the oblique waves. However, the plane wave continues to follow the linear theory, even when the oblique waves' amplitude attains the same order of magnitude as that of the plane wave. A fully interactive stage then comes into effect when the oblique waves exceed a certain level compared to that of the plane wave. The oblique waves react back on the fundamental, slowing its growth rate. The oblique waves' saturation results from their self-interaction - a mechanism that does not require the presence of the plane wave. The oblique waves' saturation level is independent of their initial level, but decreases as the obliqueness angle increases.
Interharmonic modulation products as a means to quantify nonlinear D-region interactions
NASA Astrophysics Data System (ADS)
Moore, Robert
Experimental observations performed during dual beam ionospheric HF heating experiments at the High frequency Active Auroral Research Program (HAARP) HF transmitter in Gakona, Alaska are used to quantify the relative importance of specific nonlinear interactions that occur within the D region ionosphere. During these experiments, HAARP broadcast two amplitude modulated HF beams whose center frequencies were separated by less than 20 kHz. One beam was sinusoidally modulated at 500 Hz while the second beam was sinusoidally modulated using a 1-7 kHz linear frequency-time chirp. ELF/VLF observations performed at two different locations (3 and 98 km from HAARP) provide clear evidence of strong interactions between all field components of the two HF beams in the form of low and high order interharmonic modulation products. From a theoretical standpoint, the observed interharmonic modulation products could be produced by several different nonlinearities. The two primary nonlinearities take the form of wave-medium interactions (i.e., cross modulation), wherein the ionospheric conductivity modulation produced by one signal crosses onto the other signal via collision frequency modification, and wave-wave interactions, wherein the conduction current associated with one wave mixes with the electric field of the other wave to produce electron temperature oscillations. We are able to separate and quantify these two different nonlinearities, and we conclude that the wave-wave interactions dominate the wave-medium interactions by a factor of two. These results are of great importance for the modeling of transioinospheric radio wave propagation, in that both the wave-wave and the wave-medium interactions could be responsible for a significant amount of anomalous absorption.
Beam instabilities stabilization as a result of strong nonlinear interaction between waves
Soloshenko, I.A.; Taranov, V.B.; Tsyolko, V.V.; Shamrai, K.P.; Shulzhenko, P.M. )
1990-01-01
It is shown that the nonlinear interaction between unstable low-frequency ion waves and high-frequency electron waves growing in an ion beam plasma can result in stabilization of one of the modes if the level of the other is sufficiently high. A theoretical model of the phenomenon has been developed, and its predictions are in reasonable agreement with experimental results. The suppression mechanism is considered, and appears to be essentially nonlinear. The effect of this mutual suppression of ion beam instabilities may be important for improved ion beam transport.
Nonlinear interaction of two trapped-mode resonances in a bilayer fish-scale metamaterial
NASA Astrophysics Data System (ADS)
Tuz, Vladimir R.; Novitsky, Denis V.; Mladyonov, Pavel L.; Prosvirnin, Sergey L.; Novitsky, Andrey V.
2014-09-01
We report on a bistable light transmission through a bilayer "fish-scale" (meander-line) metamaterial. It is demonstrated that an all-optical switching may be achieved nearly the frequency of the high-quality-factor Fano-shaped trapped-mode resonance excitation. The nonlinear interaction of two closely spaced trapped-mode resonances in the bilayer structure composed with a Kerr-type nonlinear dielectric slab is analyzed in both frequency and time domains. It is demonstrated that these two resonances react differently on the applied intense light which leads to destination of a multistable transmission.
Nonlinear Interaction of Elliptical Laser Beam with Collisional Plasma: Effect of Linear Absorption
NASA Astrophysics Data System (ADS)
Keshav, Walia; Sarabjit, Kaur
2016-01-01
In the present work, nonlinear interaction of elliptical laser beam with collisional plasma is studied by using paraxial ray approximation. Nonlinear differential equations for the beam width parameters of semi-major axis and semi-minor axis of elliptical laser beam have been set up and solved numerically to study the variation of beam width parameters with normalized distance of propagation. Effects of variation in absorption coefficient and plasma density on the beam width parameters are also analyzed. It is observed from the analysis that extent of self-focusing of beam increases with increase/decrease in plasma density/absorption coefficient.
NASA Astrophysics Data System (ADS)
Shen, Yanfeng; Cesnik, Carlos E. S.
2016-04-01
This paper presents a parallelized modeling technique for the efficient simulation of nonlinear ultrasonics introduced by the wave interaction with fatigue cracks. The elastodynamic wave equations with contact effects are formulated using an explicit Local Interaction Simulation Approach (LISA). The LISA formulation is extended to capture the contact-impact phenomena during the wave damage interaction based on the penalty method. A Coulomb friction model is integrated into the computation procedure to capture the stick-slip contact shear motion. The LISA procedure is coded using the Compute Unified Device Architecture (CUDA), which enables the highly parallelized supercomputing on powerful graphic cards. Both the explicit contact formulation and the parallel feature facilitates LISA's superb computational efficiency over the conventional finite element method (FEM). The theoretical formulations based on the penalty method is introduced and a guideline for the proper choice of the contact stiffness is given. The convergence behavior of the solution under various contact stiffness values is examined. A numerical benchmark problem is used to investigate the new LISA formulation and results are compared with a conventional contact finite element solution. Various nonlinear ultrasonic phenomena are successfully captured using this contact LISA formulation, including the generation of nonlinear higher harmonic responses. Nonlinear mode conversion of guided waves at fatigue cracks is also studied.
NASA Astrophysics Data System (ADS)
Nguyen, Quan Minh
2011-12-01
We investigate the propagation of solitons of the perturbed nonlinear Schrodinger equation (NLSE) via asymptotic perturbation techniques and numerical simulations. The dissertation consists of several inter-related projects [22, 98, 103, 108, 109] that are focused on the effects of nonlinear processes and randomness on dynamics of pulses of light in optical waveguides. We particularly consider two of the most important nonlinear processes affecting pulse dynamics in multichannel optical waveguides: weak cubic loss and delayed Raman response. In the presence of weak cubic loss [98], we obtain the analytic expressions for the amplitude and frequency shifts in a single two-soliton collision and show that the impact of a fast three-soliton collision is given by the sum of the two-soliton interactions. Furthermore, we show that amplitude dynamics in an N-channel waveguide system is described by a Lotka-Volterra model for N competing species. We find the conditions on the time slot width and the soliton's equilibrium amplitude value under which the transmission is stable. The predictions of the reduced Lotka-Volterra model are confirmed by numerical solution of a coupled-NLSE model, which takes into account intra-pulse and inter-pulse effects due to cubic nonlinearity and cubic loss. These results uncover an interesting analogy between the dynamics of energy exchange in pulse collisions and population dynamics in Lotka-Volterra models. In the presence of delayed Raman response [103,108,109], we show that the dynamics of pulse amplitudes in an N-channel transmission system in differential phase shift keying (DPSK) scheme is described by an N-dimensional predator-prey model. We find the equilibrium states with non-zero amplitudes and prove their stability by obtaining the Lyapunov function. We then show that stable transmission can be achieved by a proper choice of the frequency profile of linear amplifier gain. We also investigate the impact of Raman self- and collsion
Nonlinear pressure dependence of the interaction potential of dense protein solutions.
Schroer, Martin A; Markgraf, Jonas; Wieland, D C Florian; Sahle, Christoph J; Möller, Johannes; Paulus, Michael; Tolan, Metin; Winter, Roland
2011-04-29
The influence of pressure on the structure and protein-protein interaction potential of dense protein solutions was studied and analyzed using small-angle x-ray scattering in combination with a liquid state theoretical approach. The structural as well as the interaction parameters of dense lysozyme solutions are affected by pressure in a nonlinear way. The structural properties of water lead to a modification of the protein-protein interactions below 4 kbar, which might have significant consequences for the stability of proteins in extreme natural environments. PMID:21635065
Thermodynamics of ghost dark energy in case of various nonlinear interactions
NASA Astrophysics Data System (ADS)
Khurshudyan, M.
2016-05-01
In this paper we discuss thermodynamics of interacting ghost dark energy models in a flat FRW universe. During the discussion our attention will be concentrated on nonlinear interactions of particular form. In the considered models dark matter is assumed to be a pressureless matter and allows to complete the darkness of the low-redshift universe. Ghost dark energy it is one of the models of dark energy among others with an explicitly given energy density as a function of the Hubble parameter of the universe. Our study aims to have a contribution towards recently suggested interacting ghost dark energy models.
Nonlinear theory for a terahertz gyrotron with a special cross-section interaction cavity
Yuan, Xuesong; Han Yu; Yan Yang; Lan Ying
2012-05-15
The fully numerical nonlinear theory for a gyrotron with a special cross-section interaction cavity has been developed in this paper. In this theory, the analytical solution to different modes in the special cross-section interaction cavity is replaced by the numerical solution based on electromagnetic simulation results. A 0.4 THz third harmonic gyrotron with an azimuthally corrugated interaction cavity has been investigated by using this theory and simulation results show that this approach has a significant advantage of developing high harmonic terahertz gyrotrons.
Ferman, M.A.
1994-12-31
A collection of some highlights of the Author`s experiences with nonlinear dynamics in analyses and tests of Panels and Membranes encountered over the past 40 years is given. The primary focus is placed on a major block of his work since the early 70`s, involving work with fluid-structure interaction with Panels and Membranes, and with efforts in Acoustic Fatigue of Panels. While the Author had encountered nonlinear problems throughout Ins career involving flutter, vibration in general, and dynamic thrust instability; it was the more recent work with panels and membranes that greatly expanded his experience. This was triggered by the advent of highly maneuverable aircraft, powered by large powerful, noisy engines, and new materials in the mid 70`s. The significance of nonlinearity for these applications is most obvious from the results shown here-it simply cannot be ignored for optimal, safe design.
Blanloeuil, Philippe; Croxford, Anthony J; Meziane, Anissa
2014-04-01
The nonlinear interaction of shear waves with a frictional interface are presented and modeled using simple Coulomb friction. Analytical and finite difference implementations are proposed with both in agreement and showing a unique trend in terms of the generated nonlinearity. A dimensionless parameter ξ is proposed to uniquely quantify the nonlinearity produced. The trends produced in the numerical study are then validated with good agreement experimentally. This is carried out loading an interface between two steel blocks and exciting this interface with different amplitude normal incidence shear waves. The experimental results are in good agreement with the numerical results, suggesting the simple friction model does a reasonable job of capturing the fundamental physics. The resulting approach offers a potential way to characterize a contacting interface; however, the difficulty in activating that interface may ultimately limit its applicability. PMID:25234971
Chaitanya, N. Apurv; Jabir, M. V.; Banerji, J.; Samanta, G. K.
2016-01-01
Hollow Gaussian beams (HGB) are a special class of doughnut shaped beams that do not carry orbital angular momentum (OAM). Such beams have a wide range of applications in many fields including atomic optics, bio-photonics, atmospheric science, and plasma physics. Till date, these beams have been generated using linear optical elements. Here, we show a new way of generating HGBs by three-wave mixing in a nonlinear crystal. Based on nonlinear interaction of photons having OAM and conservation of OAM in nonlinear processes, we experimentally generated ultrafast HGBs of order as high as 6 and power >180 mW at 355 nm. This generic concept can be extended to any wavelength, timescales (continuous-wave and ultrafast) and any orders. We show that the removal of azimuthal phase of vortices does not produce Gaussian beam. We also propose a new and only method to characterize the order of the HGBs. PMID:27581625
Chaitanya, N Apurv; Jabir, M V; Banerji, J; Samanta, G K
2016-01-01
Hollow Gaussian beams (HGB) are a special class of doughnut shaped beams that do not carry orbital angular momentum (OAM). Such beams have a wide range of applications in many fields including atomic optics, bio-photonics, atmospheric science, and plasma physics. Till date, these beams have been generated using linear optical elements. Here, we show a new way of generating HGBs by three-wave mixing in a nonlinear crystal. Based on nonlinear interaction of photons having OAM and conservation of OAM in nonlinear processes, we experimentally generated ultrafast HGBs of order as high as 6 and power >180 mW at 355 nm. This generic concept can be extended to any wavelength, timescales (continuous-wave and ultrafast) and any orders. We show that the removal of azimuthal phase of vortices does not produce Gaussian beam. We also propose a new and only method to characterize the order of the HGBs. PMID:27581625
Nonlinear Jaynes–Cummings model for two interacting two-level atoms
NASA Astrophysics Data System (ADS)
de los Santos-Sánchez, O.; González-Gutiérrez, C.; Récamier, J.
2016-08-01
In this work we examine a nonlinear version of the Jaynes–Cummings model for two identical two-level atoms allowing for Ising-like and dipole–dipole interplays between them. The model is said to be nonlinear in the sense that it can incorporate both a general intensity-dependent interaction between the atomic system and the cavity field and/or the presence of a nonlinear medium inside the cavity. As an example, we consider a particular type of atom-field coupling based upon the so-called Buck–Sukumar model and a lossless Kerr-like cavity. We describe the possible effects of such features on the evolution of some quantities of current interest, such as atomic excitation, purity, concurrence, the entropy of the field and the evolution of the latter in phase space.
Nonlinear interaction of kinetic Alfvén waves and ion acoustic waves in coronal loops
NASA Astrophysics Data System (ADS)
Sharma, Prachi; Yadav, Nitin; Sharma, R. P.
2016-05-01
Over the years, coronal heating has been the most fascinating question among the scientific community. In the present article, a heating mechanism has been proposed based on the wave-wave interaction. Under this wave-wave interaction, the high frequency kinetic Alfvén wave interacts with the low frequency ion acoustic wave. These waves are three dimensionally propagating and nonlinearly coupled through ponderomotive nonlinearity. A numerical code based on pseudo-spectral technique has been developed for solving these normalized dynamical equations. Localization of kinetic Alfvén wave field has been examined, and magnetic power spectrum has also been analyzed which shows the cascading of energy to higher wavenumbers, and this cascading has been found to have Kolmogorov scaling, i.e., k-5 /3 . A breakpoint appears after Kolmogorov scaling and next to this spectral break; a steeper scaling has been obtained. The presented nonlinear interaction for coronal loops plasmas is suggested to generate turbulent spectrum having Kolmogorov scaling in the inertial range and steepened scaling in the dissipation range. Since Kolmogorov turbulence is considered as the main source for coronal heating; therefore, the suggested mechanism will be a useful tool to understand the mystery of coronal loop heating through Kolmogorov turbulence and dissipation.
On the efficacy of friction damping in the presence of nonlinear modal interactions
NASA Astrophysics Data System (ADS)
Krack, Malte; Bergman, Lawrence A.; Vakakis, Alexander F.
2016-05-01
This work addresses friction-induced modal interactions in jointed structures, and their effects on the passive mitigation of vibrations by means of friction damping. Under the condition of (nearly) commensurable natural frequencies, the nonlinear character of friction can cause so-called nonlinear modal interactions. If harmonic forcing near the natural frequency of a specific mode is applied, for instance, another mode may be excited due to nonlinear energy transfer and thus contribute considerably to the vibration response. We investigate how this phenomenon affects the performance of friction damping. To this end, we study the steady-state, periodic forced vibrations of a system of two beams connected via a local mechanical friction joint. The system can be tuned to continuously adjust the ratio between the first two natural frequencies in the range around the 1:3 internal resonance, in order to trigger or suppress the emergence of modal interactions. Due to the re-distribution of the vibration energy, the vibration level can in fact be reduced in certain situations. However, in other situations, the multi-harmonic character of the vibration has detrimental effects on the effective damping provided by the friction joint. The resulting response level can be significantly larger than in the absence of modal interactions. Moreover, it is shown that the vibration behavior is highly sensitive in the neighborhood of internal resonances. It is thus concluded that the condition of internal resonance should be avoided in the design of friction-damped systems.
Wave-vortex interactions in the nonlinear Schrödinger equation
NASA Astrophysics Data System (ADS)
Guo, Yuan; Bühler, Oliver
2014-02-01
This is a theoretical study of wave-vortex interaction effects in the two-dimensional nonlinear Schrödinger equation, which is a useful conceptual model for the limiting dynamics of superfluid quantum condensates at zero temperature. The particular wave-vortex interaction effects are associated with the scattering and refraction of small-scale linear waves by the straining flows induced by quantized point vortices and, crucially, with the concomitant nonlinear back-reaction, the remote recoil, that these scattered waves exert on the vortices. Our detailed model is a narrow, slowly varying wavetrain of small-amplitude waves refracted by one or two vortices. Weak interactions are studied using a suitable perturbation method in which the nonlinear recoil force on the vortex then arises at second order in wave amplitude, and is computed in terms of a Magnus-type force expression for both finite and infinite wavetrains. In the case of an infinite wavetrain, an explicit asymptotic formula for the scattering angle is also derived and cross-checked against numerical ray tracing. Finally, under suitable conditions a wavetrain can be so strongly refracted that it collapses all the way onto a zero-size point vortex. This is a strong wave-vortex interaction by definition. The conditions for such a collapse are derived and the validity of ray tracing theory during the singular collapse is investigated.
Nonlinear tearing mode interactions and mode locking in reversed field pinches
Hegna, C.C.
1996-06-01
The nonlinear interaction of a set of tearing instabilities and plasma flow is studied in a cylindrical plasma. An analytic theory of mode locking is developed which includes the effects of the localized electromagnetic torques, plasma inertia and cross-field viscosity. The calculation is specialized for the case of mode locking on the Madison Symmetric Torus (MST) reversed field pinch. In MST plasmas, a set of m = 1 tearing instabilities become phase locked and form a toroidally localized, rotating magnetic disturbance. An evolution equation for the phase velocity of this magnetic disturbance is derived which accounts for two types of electromagnetic torques. The external torques describe the interaction of the tearing modes with static magnetic perturbations located outside the plasma region. The interior torques describe the nonlinear interaction of three tearing modes which satisfy a wave number resonance condition. For conditions typical of MST, the internal torques dominate the external torques, which suggest the nonlinear interaction of tearing instabilities play a prominent role in the momentum degradation and mode locking.
Wave–vortex interactions in the nonlinear Schrödinger equation
Guo, Yuan Bühler, Oliver
2014-02-15
This is a theoretical study of wave–vortex interaction effects in the two-dimensional nonlinear Schrödinger equation, which is a useful conceptual model for the limiting dynamics of superfluid quantum condensates at zero temperature. The particular wave–vortex interaction effects are associated with the scattering and refraction of small-scale linear waves by the straining flows induced by quantized point vortices and, crucially, with the concomitant nonlinear back-reaction, the remote recoil, that these scattered waves exert on the vortices. Our detailed model is a narrow, slowly varying wavetrain of small-amplitude waves refracted by one or two vortices. Weak interactions are studied using a suitable perturbation method in which the nonlinear recoil force on the vortex then arises at second order in wave amplitude, and is computed in terms of a Magnus-type force expression for both finite and infinite wavetrains. In the case of an infinite wavetrain, an explicit asymptotic formula for the scattering angle is also derived and cross-checked against numerical ray tracing. Finally, under suitable conditions a wavetrain can be so strongly refracted that it collapses all the way onto a zero-size point vortex. This is a strong wave–vortex interaction by definition. The conditions for such a collapse are derived and the validity of ray tracing theory during the singular collapse is investigated.
Pitch glide effect induced by a nonlinear string-barrier interaction
NASA Astrophysics Data System (ADS)
Kartofelev, Dmitri; Stulov, Anatoli; Välimäki, Vesa
2015-10-01
Interactions of a vibrating string with its supports and other spatially distributed barriers play a significant role in the physics of many stringed musical instruments. It is well known that the tone of the string vibrations is determined by the string supports, and that the boundary conditions of the string termination may cause a short-lasting initial fundamental frequency shifting. Generally, this phenomenon is associated with the nonlinear modulation of the stiff string tension. The aim of this paper is to study the initial frequency glide phenomenon that is induced only by the string-barrier interaction, apart from other possible physical causes, and without the interfering effects of dissipation and dispersion. From a numerical simulation perspective, this highly nonlinear problem may present various difficulties, not the least of which is the risk of numerical instability. We propose a numerically stable and a purely kinematic model of the string-barrier interaction, which is based on the travelling wave solution of the ideal string vibration. The model is capable of reproducing the motion of the vibrating string exhibiting the initial fundamental frequency glide, which is caused solely by the complex nonlinear interaction of the string with its termination. The results presented in this paper can expand our knowledge and understanding of the timbre evolution and the physical principles of sound generation of numerous stringed instruments, such as lutes called the tambura, sitar and biwa.
Su, Zhenpeng Zhu, Hui; Zheng, Huinan; Xiao, Fuliang; Zhang, Min; Liu, Y. C.-M.; Shen, Chao; Wang, Yuming; Wang, Shui
2014-05-15
Electromagnetic ion cyclotron (EMIC) waves can lead to the rapid decay (on a timescale of hours) of the terrestrial ring current. Such decay process is usually investigated in the framework of quasi-linear theory. Here, both theoretical analysis and test-particle simulation are performed to understand the nonlinear interaction between ring current ions and EMIC waves. In particular, the dependence of the nonlinear wave-particle interaction processes on the ion initial latitude is investigated in detail. These nonlinear processes are classified into the phase trapping and phase bunching, and the phase bunching is further divided into the channel and cluster effects. Compared to the prediction of the quasi-linear theory, the ring current decay rate can be reduced by the phase trapping, increased by the channel effect phase bunching, but non-deterministically influenced by the cluster effect phase bunching. The ion initial latitude changes the occurrence of the phase trapping, modulates the transport direction and strength of the cluster effect phase bunching, and only slightly affects the channel effect phase bunching. The current results suggest that the latitudinal dependence of these nonlinear processes should be considered in the evaluation of the ring current decay induced by EMIC waves.
Siminos, E; Sánchez-Arriaga, G; Saxena, V; Kourakis, I
2014-12-01
We investigate the dynamics of localized solutions of the relativistic cold-fluid plasma model in the small but finite amplitude limit, for slightly overcritical plasma density. Adopting a multiple scale analysis, we derive a perturbed nonlinear Schrödinger equation that describes the evolution of the envelope of circularly polarized electromagnetic field. Retaining terms up to fifth order in the small perturbation parameter, we derive a self-consistent framework for the description of the plasma response in the presence of localized electromagnetic field. The formalism is applied to standing electromagnetic soliton interactions and the results are validated by simulations of the full cold-fluid model. To lowest order, a cubic nonlinear Schrödinger equation with a focusing nonlinearity is recovered. Classical quasiparticle theory is used to obtain analytical estimates for the collision time and minimum distance of approach between solitons. For larger soliton amplitudes the inclusion of the fifth-order terms is essential for a qualitatively correct description of soliton interactions. The defocusing quintic nonlinearity leads to inelastic soliton collisions, while bound states of solitons do not persist under perturbations in the initial phase or amplitude. PMID:25615203
Quantum transport of strongly interacting photons in a one-dimensional nonlinear waveguide
NASA Astrophysics Data System (ADS)
Hafezi, Mohammad; Chang, Darrick E.; Gritsev, Vladimir; Demler, Eugene; Lukin, Mikhail D.
2012-01-01
We present a theoretical technique for solving the quantum transport problem of a few photons through a one-dimensional, strongly nonlinear waveguide. We specifically consider the situation where the evolution of the optical field is governed by the quantum nonlinear Schrödinger equation. Although this kind of nonlinearity is quite general, we focus on a realistic implementation involving cold atoms loaded in a hollow-core optical fiber, where the atomic system provides a tunable nonlinearity that can be large even at a single-photon level. In particular, we show that when the interaction between photons is effectively repulsive, the transmission of multiphoton components of the field is suppressed. This leads to antibunching of the transmitted light and indicates that the system acts as a single-photon switch. On the other hand, in the case of attractive interaction, the system can exhibit either antibunching or bunching, which is in stark contrast to semiclassical calculations. We show that the bunching behavior is related to the resonant excitation of bound states of photons inside the system.
Nonlinear soil-structure interaction analysis of SIMQUAKE II. Final report
Vaughan, D.K.; Isenberg, J.
1982-04-01
This report describes an analytic method for modeling of soil-structure interaction (SSI) for nuclear power plants in earthquakes and discusses its application to SSI analyses of SIMQUAKE II. The method is general and can be used to simulate a three-dimensional structural geometry, nonlinear site characteristics and arbitrary input ground shaking. The analytic approach uses the soil island concept to reduce SSI models to manageable size and cost. Nonlinear constitutive behavior of the soil is represented by the nonlinear, kinematic cap model. In addition, a debonding-rebonding soil-structure interface model is utilized to represent nonlinear effects which singificantly alter structural response in the SIMQUAKE tests. STEALTH, an explicit finite difference code, is used to perform the dynamic, soil-structure interaction analyses. Several two-dimensional posttest SSI analyses of model containment structures in SIMQUAKE II are performed and results compared with measured data. These analyses qualify the analytic method. They also show the importance of including debonding-rebonding at the soil-structure interface. Sensitivity of structural response to compaction characteristics of backfill material is indicated.
Li, Shourui; Wang, Kai; Zhou, Mi; Li, Qian; Liu, Bingbing; Zou, Guangtian; Zou, Bo
2012-02-06
We report the results of high-pressure Raman and X-ray diffraction measurements performed on ammonium squarate ((NH{sub 4}){sub 2}C{sub 4}O{sub 4}, AS), a representative supramolecular architecture based on hydrogen bonding and {pi}-stacking interactions, at various pressures up to 19 GPa. Two phase transitions at 2.7 GPa and in the pressure range of 11.1-13.6 GPa were observed. Both Raman and XRD results provide convincing evidence for these two phase transitions. The first phase transition is attributed to the rearrangements of hydrogen-bonding networks, resulting in the symmetry transformation from P2{sub 1}/c to P1. The second one, which is identified as an order-disorder phase transition, arises from significant modifications of squarate rings and random orientations of NH{sub 4}{sup +} cations. The cooperative effects between hydrogen-bonding and {pi}-stacking interactions, as well as mechanisms for the phase transitions, are discussed by virtue of the local structure of AS.
Li, Ji; Li, You; Zhang, Wenting; Chen, Zhao; Fan, Guorong
2013-06-01
A simple, sensitive and low-cost method using CE coupled with glucose-β-CD interaction assisted ACN stacking technique has been developed for quantification of trace amlodipine in dog plasma. The plasma samples were extracted with methyl tert-butyl ether. The separation was performed at 25°C in a 31.2 cm × 75 μm fused-silica capillary with an applied voltage of 15 kV. The BGE was composed of 6.25 mM borate/25 mM phosphate (pH 2.5) and 5 mg/mL glucose-β-CD. The detection wavelength was 200 nm. Because CD could diminish the interaction between drugs and matrix, and derivation groups of CD play an important role in separation performance, the effects of β-CD, and its derivatives on the separation were studied at several concentrations (0, 2.5, 5.0, 10.0 mg/mL). In this study, organic solvent field-amplified sample stacking technique in combination with glucose-β-CD enhanced the sensitivity about 60-70 folds and glucose-β-CD could effectively improve the peak shape. All the validation data, such as accuracy, precision extraction recovery, and stability, were within the required limits. The calibration curve was linear for amlodipine from 1 to 200 ng/mL. The method developed was successfully applied to the pharmacokinetic studies of amlodipine besylate in beagle dogs. PMID:23495256
NASA Astrophysics Data System (ADS)
Randrianandrasana, Michel F.; Wei, Xueyong; Lowe, David
2011-07-01
Future sensor arrays will be composed of interacting nonlinear components with complex behaviours with no known analytic solutions. This paper provides a preliminary insight into the expected behaviour through numerical and analytical analysis. Specifically, the complex behaviour of a periodically driven nonlinear Duffing resonator coupled elastically to a van der Pol oscillator is investigated as a building block in a 2D lattice of such units with local connectivity. An analytic treatment of the 2-device unit is provided through a two-time-scales approach and the stability of the complex dynamic motion is analysed. The pattern formation characteristics of a 2D lattice composed of these units coupled together through nearest neighbour interactions is analysed numerically for parameters appropriate to a physical realisation through MEMS devices. The emergent patterns of global and cluster synchronisation are investigated with respect to system parameters and lattice size.
NASA Astrophysics Data System (ADS)
Roy, Barna; Kumar, Nand Kishor; Nambissan, Padinharu Madathil Gopalakrishnan; Das, Jayanta
2014-06-01
The effect of cryorolling (CR) strain at 153 K on the evolution of structural defects and their interaction in α-brass (Cu-30 wt.% Zn) during nanostructuring has been evaluated. Even though the lattice strain increases up to 2.1 × 10-3 at CR strain of 0.6 initially, but it remains constant upon further rolling. Whereas, the twin density (β) increases to a maximum value of 5.9 × 10-3 at a CR strain of 0.7 and reduces to 1.1 × 10-5 at 0.95. Accumulation of stacking faults (SFs) and lattice disorder at the twin boundaries causes dynamic recrystallization, promotes grain refinement and decreases the twin density by forming subgrains. Detailed investigations on the formation and interaction of defects have been done through resistivity, positron lifetime and Doppler broadening measurements in order to understand the micro-mechanism of nanostructuring at sub-zero temperatures.
Interaction between turbulence and a nonlinear tearing mode in the low {beta} regime
Militello, F.; Waelbroeck, F. L.; Fitzpatrick, R.; Horton, W.
2008-05-15
The interaction between turbulence and a nonlinear tearing mode is investigated numerically using a 2D electrostatic model. Turbulence is found to cause transitions between the different roots for the propagation velocity of the mode. The transitions take the mode towards roots with slower propagation that are characterized by a locally flattened density profile. For sufficiently large islands the transition reduces the drive for the tearing mode.
Christophersen, A; McKinley-McKee, J S
1984-01-01
An interactive program for analysing enzyme activity-time data using non-linear regression analysis is described. Protection studies can also be dealt with. The program computes inactivation rates, dissociation constants and promotion or inhibition parameters with their standard errors. It can also be used to distinguish different inactivation models. The program is written in SIMULA and is menu-oriented for refining or correcting data at the different levels of computing. PMID:6546558
Nonlinear spectroscopic effects in quantum gases induced by atom-atom interactions
Safonov, A. I. Safonova, I. I.; Yasnikov, I. S.
2013-05-15
We consider nonlinear spectroscopic effects-interaction-enhanced double resonance and spectrum instability-that appear in ultracold quantum gases owing to collisional frequency shift of atomic transitions and, consequently, due to the dependence of the frequencies on the population of various internal states of the particles. Special emphasis is put to two simplest cases, (a) the gas of two-level atoms and (b) double resonance in a gas of three-level bosons, in which the probe transition frequency remains constant.
The Effect of Crack Orientation on the Nonlinear Interaction of a P-wave with an S-wave
TenCate, J. A.; Malcolm, A. E.; Feng, X.; Fehler, M. C.
2016-06-06
Cracks, joints, fluids, and other pore-scale structures have long been hypothesized to be the cause of the large elastic nonlinearity observed in rocks. It is difficult to definitively say which pore-scale features are most important, however, because of the difficulty in isolating the source of the nonlinear interaction. In this work, we focus on the influence of cracks on the recorded nonlinear signal and in particular on how the orientation of microcracks changes the strength of the nonlinear interaction. We do this by studying the effect of orientation on the measurements in a rock with anisotropy correlated with the presencemore » and alignment of microcracks. We measure the nonlinear response via the traveltime delay induced in a low-amplitude P wave probe by a high-amplitude S wave pump. We find evidence that crack orientation has a significant effect on the nonlinear signal.« less
The effect of crack orientation on the nonlinear interaction of a P wave with an S wave
NASA Astrophysics Data System (ADS)
TenCate, J. A.; Malcolm, A. E.; Feng, X.; Fehler, M. C.
2016-06-01
Cracks, joints, fluids, and other pore-scale structures have long been hypothesized to be the cause of the large elastic nonlinearity observed in rocks. It is difficult to definitively say which pore-scale features are most important, however, because of the difficulty in isolating the source of the nonlinear interaction. In this work, we focus on the influence of cracks on the recorded nonlinear signal and in particular on how the orientation of microcracks changes the strength of the nonlinear interaction. We do this by studying the effect of orientation on the measurements in a rock with anisotropy correlated with the presence and alignment of microcracks. We measure the nonlinear response via the traveltime delay induced in a low-amplitude P wave probe by a high-amplitude S wave pump. We find evidence that crack orientation has a significant effect on the nonlinear signal.
NASA Astrophysics Data System (ADS)
Gevorgyan, A. H.
2015-12-01
Resonance properties of a stack consisting of a cholesteric liquid crystal and isotropic medium layers are investigated. Bragg's conditions for photonic band gaps are presented for the considered system. It is shown that a significant control of the system zone structure is possible in the case of a proper selection of the sublayer parameters. It is also shown that an effect of complete suppression of absorption is not usually observed in the case of anisotropic absorption in cholesteric liquid crystal sublayers. The possibility to achieve this effect in the considered system, imposing certain conditions on the thickness and the refraction index of the isotropic medium sublayers, is shown. Also, it is shown that in such conditions a large increase of the maximum of photonic density of states happens at the appropriate zone borders.
Nonlinear instability and chaos in plasma wave-wave interactions, I., Introduction
Kueny, C.S.; Morrison, P.J.
1994-11-01
Conventional linear stability analyses may fail for fluid systems with an indefinite free energy functional. When such a system is linearly stable, it is said to possess negative energy modes. Instability may then occur either via dissipation of the negative energy modes, or nonlinearly via resonant wave-wave coupling, leading to explosive growth. In the dissipationless case, it is conjectured that intrinsic chaotic behavior may allow initially nonresonant systems to reach resonance by diffusion in phase space. In this and a companion paper [submitted to Physics of Plasmas], this phenomenon is demonstrated for a simple equilibrium involving cold counterstreaming ions. The system is described in the fluid approximation by a Hamiltonian functional and associated noncanonical Poisson bracket. By Fourier decomposition and appropriate coordinate transformations, the Hamiltonian for the perturbed energy is expressed in action-angle form. The normal modes correspond to Doppler-shifted ion-acoustic waves of positive and negative energy. Nonlinear coupling leads to decay instability via two-wave interactions, and to either decay or explosive instability via three-wave interactions. These instabilities are described for various (integrable) systems of waves interacting via single nonlinear terms. This discussion provides the foundation for the treatment of nonintegrable systems in the companion paper.
Tewarie, P.; Bright, M.G.; Hillebrand, A.; Robson, S.E.; Gascoyne, L.E.; Morris, P.G.; Meier, J.; Van Mieghem, P.; Brookes, M.J.
2016-01-01
Understanding the electrophysiological basis of resting state networks (RSNs) in the human brain is a critical step towards elucidating how inter-areal connectivity supports healthy brain function. In recent years, the relationship between RSNs (typically measured using haemodynamic signals) and electrophysiology has been explored using functional Magnetic Resonance Imaging (fMRI) and magnetoencephalography (MEG). Significant progress has been made, with similar spatial structure observable in both modalities. However, there is a pressing need to understand this relationship beyond simple visual similarity of RSN patterns. Here, we introduce a mathematical model to predict fMRI-based RSNs using MEG. Our unique model, based upon a multivariate Taylor series, incorporates both phase and amplitude based MEG connectivity metrics, as well as linear and non-linear interactions within and between neural oscillations measured in multiple frequency bands. We show that including non-linear interactions, multiple frequency bands and cross-frequency terms significantly improves fMRI network prediction. This shows that fMRI connectivity is not only the result of direct electrophysiological connections, but is also driven by the overlap of connectivity profiles between separate regions. Our results indicate that a complete understanding of the electrophysiological basis of RSNs goes beyond simple frequency-specific analysis, and further exploration of non-linear and cross-frequency interactions will shed new light on distributed network connectivity, and its perturbation in pathology. PMID:26827811
Influence of cross-flow on nonlinear Tollmien-Schlichting/vortex interaction
NASA Technical Reports Server (NTRS)
Davis, D. A. R.; Smith, F. T.
1994-01-01
The transition of an incompressible three-dimensional boundary layer with strong cross-flow is considered theoretically and computationally in the context of vortex/wave interactions. Specifically the work centers on two lower-branch Tollmien-Schlichting waves which mutually interact nonlinearly to induce a longitudinal vortex flow. The vortex motion in turn gives rise to significant wave modulation via wall-shear forcing. The characteristic Reynolds number is large and, as a consequence, the waves' and the vortex motion are governed primarily by triple deck theory. The nonlinear interaction is captured by a viscous partial-differential system for the vortex coupled with a pair of amplitude equations for each wave pressure. Following analysis and computation over a wide range of parameters, three distinct responses are found to emerge in the nonlinear behavior of the flow solution downstream: an algebraic finite-distance singularity, far-downstream saturation or far-downstream wave decay leaving pure vortex flow. These depend on the input conditions, the wave angles and the size of the cross flow.
Tewarie, P; Bright, M G; Hillebrand, A; Robson, S E; Gascoyne, L E; Morris, P G; Meier, J; Van Mieghem, P; Brookes, M J
2016-04-15
Understanding the electrophysiological basis of resting state networks (RSNs) in the human brain is a critical step towards elucidating how inter-areal connectivity supports healthy brain function. In recent years, the relationship between RSNs (typically measured using haemodynamic signals) and electrophysiology has been explored using functional Magnetic Resonance Imaging (fMRI) and magnetoencephalography (MEG). Significant progress has been made, with similar spatial structure observable in both modalities. However, there is a pressing need to understand this relationship beyond simple visual similarity of RSN patterns. Here, we introduce a mathematical model to predict fMRI-based RSNs using MEG. Our unique model, based upon a multivariate Taylor series, incorporates both phase and amplitude based MEG connectivity metrics, as well as linear and non-linear interactions within and between neural oscillations measured in multiple frequency bands. We show that including non-linear interactions, multiple frequency bands and cross-frequency terms significantly improves fMRI network prediction. This shows that fMRI connectivity is not only the result of direct electrophysiological connections, but is also driven by the overlap of connectivity profiles between separate regions. Our results indicate that a complete understanding of the electrophysiological basis of RSNs goes beyond simple frequency-specific analysis, and further exploration of non-linear and cross-frequency interactions will shed new light on distributed network connectivity, and its perturbation in pathology. PMID:26827811
Anharmonic stacking in supercoiled DNA
NASA Astrophysics Data System (ADS)
Zoli, Marco
2012-05-01
Multistep denaturation in a short circular DNA molecule is analyzed by a mesoscopic Hamiltonian model which accounts for the helicoidal geometry. Computation of melting profiles by the path integral method suggests that stacking anharmonicity stabilizes the double helix against thermal disruption of the hydrogen bonds. Twisting is essential in the model to capture the importance of nonlinear effects on the thermodynamical properties. In a ladder model with zero twist, anharmonic stacking scarcely affects the thermodynamics. Moderately untwisted helices, with respect to the equilibrium conformation, show an energetic advantage against the overtwisted ones. Accordingly moderately untwisted helices better sustain local fluctuational openings and make more unlikely the thermally driven complete strand separation.
Some non-linear interactions in polytropic gas cosmology: phase space analysis
NASA Astrophysics Data System (ADS)
Khurshudyan, Martiros
2015-11-01
There are various cosmological models with polytropic equation of state associated to dark energy. Polytropic EoS has important applications in astrophysics, therefore a study of it on cosmological framework continues to be interesting. From the other hand, there are various forms of interactions phenomenologically involved into the darkness of the universe able to solve important cosmological problems. This is a motivation for us to perform a phase space analysis of various cosmological scenarios where non-linear interacting polytropic gas models are involved. Dark matter is taken to be a pressureless fluid.
Soliton interactions and complexes for coupled nonlinear Schrödinger equations.
Jiang, Yan; Tian, Bo; Liu, Wen-Jun; Sun, Kun; Li, Min; Wang, Pan
2012-03-01
Under investigation in this paper are the coupled nonlinear Schrödinger (CNLS) equations, which can be used to govern the optical-soliton propagation and interaction in such optical media as the multimode fibers, fiber arrays, and birefringent fibers. By taking the 3-CNLS equations as an example for the N-CNLS ones (N≥3), we derive the analytic mixed-type two- and three-soliton solutions in more general forms than those obtained in the previous studies with the Hirota method and symbolic computation. With the choice of parameters for those soliton solutions, soliton interactions and complexes are investigated through the asymptotic and graphic analysis. Soliton interactions and complexes with the bound dark solitons in a mode or two modes are observed, including that (i) the two bright solitons display the breatherlike structures while the two dark ones stay parallel, (ii) the two bright and dark solitons all stay parallel, and (iii) the states of the bound solitons change from the breatherlike structures to the parallel one even with the distance between those solitons smaller than that before the interaction with the regular one soliton. Asymptotic analysis is also used to investigate the elastic and inelastic interactions between the bound solitons and the regular one soliton. Furthermore, some discussions are extended to the N-CNLS equations (N>3). Our results might be helpful in such applications as the soliton switch, optical computing, and soliton amplification in the nonlinear optics. PMID:22587200
NASA Astrophysics Data System (ADS)
Richards, Gordon R.
The succession of ice ages and interglacials during the late Pleistocene has been linked with changes in the eccentricity, obliquity and precession of the earth's orbit. The combined effect of orbital cycles with different periodicities argues that climate should exhibit both persistence — significant dependence between observations at distant intervals — and non-linearity. At the same time, a significant component of climatic variation derives from endogenous interactions which exhibit non-linear properties at both higher and lower frequencies than the orbital variations. In order to analyze the effect of orbital shifts and endogenous interactions, climate is factored into an orbitally forced and a residual component. The component explained by orbital forcing shows some evidence of non-linearity, strong dependence between observations over the first 10 ka, and additional dependence between observations at frequencies corresponding to the orbital cycles. The residual component shows greater dependence between observations over the first 20 ka, some evidence of dependence at the orbital cycles, and significantly greater degrees of non-linearity. Neither shows evidence of actual chaoticity. The climatic residual generally moves in the same direction as the path implied by orbital forcing, meaning that endogenous interactions reinforce and accentuate changes in climate implied by orbital shifts. Despite the high variability of the residual, orbital forcing acts as a long-run attractor both for temperature and for atmospheric CO 2. Actual temperatures converge to the path implied by orbital forcing, on average within a period of 7.14 ka. Because orbital forcing is a long-term attractor for temperature but short-term movements show strong serial dependence, the best forecasts for Pleistocene climate are obtained from a model including distributed lags of both orbital shifts and temperature.
Characterizing the nonlinear interaction of S- and P-waves in a rock sample
NASA Astrophysics Data System (ADS)
Gallot, Thomas; Malcolm, Alison; Szabo, Thomas L.; Brown, Stephen; Burns, Daniel; Fehler, Michael
2015-01-01
The nonlinear elastic response of rocks is known to be caused by the rocks' microstructure, particularly cracks and fluids. This paper presents a method for characterizing the nonlinearity of rocks in a laboratory scale experiment with a unique configuration. This configuration has been designed to open up the possibility of using the nonlinear characterization of rocks as an imaging tool in the field. In our experiment, we study the nonlinear interaction of two traveling waves: a low-amplitude 500 kHz P-wave probe and a high-amplitude 50 kHz S-wave pump in a room-dry 15 × 15 × 3 cm slab of Berea sandstone. Changes in the arrival time of the P-wave probe as it passes through the perturbation created by the traveling S-wave pump were recorded. Waveforms were time gated to simulate a semi-infinite medium. The shear wave phase relative to the P-wave probe signal was varied with resultant changes in the P-wave probe arrival time of up to 100 ns, corresponding to a change in elastic properties of 0.2%. In order to estimate the strain in our sample, we also measured the particle velocity at the sample surface to scale a finite difference linear elastic simulation to estimate the complex strain field in the sample, on the order of 10-6, induced by the S-wave pump. We derived a fourth order elastic model to relate the changes in elasticity to the pump strain components. We recover quadratic and cubic nonlinear parameters: β ˜ = - 872 and δ ˜ = - 1.1 × 10 10 , respectively, at room-temperature and when particle motions of the pump and probe waves are aligned. Temperature fluctuations are correlated to changes in the recovered values of β ˜ and δ ˜ , and we find that the nonlinear parameter changes when the particle motions are orthogonal. No evidence of slow dynamics was seen in our measurements. The same experimental configuration, when applied to Lucite and aluminum, produced no measurable nonlinear effects. In summary, a method of selectively determining the
NASA Astrophysics Data System (ADS)
Saeed, Aamer; Ashraf, Saba; Flörke, Ulrich; Delgado Espinoza, Zuly Yuliana; Erben, Mauricio F.; Pérez, Hiram
2016-05-01
The structure of 1-(2-oxo-2H-chromene-3-carbonyl)-3-(2-methoxy-phenyl)thiourea (1) has been determined by single-crystal X-ray crystallography. This compound crystallizes in the monoclinic space group P21/c with a = 7.455 (2) Å, b = 12.744 (3) Å, c = 16.892 (4) Å, β = 90.203 (6)° and Z = 4. Both, the coumarin and the phenyl rings are nearly coplanar with the central 1-acylthiourea group, with the Cdbnd O and Cdbnd S bonds adopting an opposite orientation. Intramolecular N-H···O, C-H···O, and C-H···S hydrogen bonds are favored by the planar conformation. The molecules are packed through C-H···O, C-H···S and C-H···C hydrogen bonds, and two π···π interactions with offset arrangement. Inter-centroid distance of 3.490 (2) Å, slip angles of 18.5 and 20.9°, and vertical displacements of 1.10 and 1.24 Å are the stacking parameters corresponding to the stronger π···π interaction. Hirshfeld surface analysis was performed for visualizing, exploring and quantifying intermolecular interactions in the crystal lattice of compound 1, and compared with two closely related species. Shape index and Curvedness surfaces indicated π-stacking with different features in opposed sides of the molecule. Fingerprint plot showed C···C contacts with similar contributions to the crystal packing in comparison with those associated to hydrogen bonds. Enrichment ratios for H···H, O···H, S···H and C···C contacts revealed a high propensity to form in the crystal.
Sorsche, Dieter; Schaub, Markus; Heinemann, Frank W; Habermehl, Johannes; Kuhri, Susanne; Guldi, Dirk; Guthmuller, Julien; Rau, Sven
2016-08-01
The synthesis and characterization of a mixed metal ruthenium(ii)/gold(iii) complex bridged by tetrapyridophenazine (tpphz) are described. It is isostructural and isoelectronic to the well-known photocatalysts with palladium(ii) or platinum(ii). Concentration dependent (1)H-NMR spectroscopy and XRD studies show that the electrostatic repulsion between the gold(iii) moieties exceeds the attractive π-stacking interaction. Theoretical calculations based on the new structural data confirm an increased positive charge on the bridging ligand as well as significantly altered orbital symmetry as compared to the previously investigated palladium(ii) complex. This is the first example of a tpphz ruthenium(ii) complex where π-stacking is completely inhibited. The detailed investigation of the solid-state structure showed for the first time in bimetallic tpphz bridged complexes no significant torsion within the bridging ligand itself. Although catalytic performance for proton reduction by gold(iii) is naturally not observed, its photochemical decomposition in colloidal gold particles could be shown by TEM and DLS. PMID:27472004
Ion scale nonlinear interaction triggered by disparate scale electron temperature gradient mode
NASA Astrophysics Data System (ADS)
Moon, Chanho; Kobayashi, Tatsuya; Itoh, Kimitaka; Hatakeyama, Rikizo; Kaneko, Toshiro
2015-05-01
We have observed that the disparate scale nonlinear interactions between the high-frequency (˜0.4 MHz) electron temperature gradient (ETG) mode and the ion-scale low-frequency fluctuations (˜kHz) were enhanced when the amplitude of the ETG mode exceeded a certain threshold. The dynamics of nonlinear coupling between the ETG mode and the drift wave (DW) mode has already been reported [C. Moon, T. Kaneko, and R. Hatakeyama, Phys. Rev. Lett. (2013)]. Here, we have newly observed that another low-frequency fluctuation with f ≃ 3.6 kHz, i.e., the flute mode, was enhanced, corresponding to the saturation of the DW mode growth. Specifically, the bicoherence between the flute mode and the DW mode reaches a significant level when the ∇Te/Te strength exceeded 0.54 cm-1. Thus, it is shown that the ETG mode energy was transferred to the DW mode, and then the energy was ultimately transferred to the flute mode, which was triggered by the disparate scale nonlinear interactions between the ETG and ion-scale low-frequency modes.
Ion scale nonlinear interaction triggered by disparate scale electron temperature gradient mode
Moon, Chanho; Kobayashi, Tatsuya; Itoh, Kimitaka; Hatakeyama, Rikizo; Kaneko, Toshiro
2015-05-15
We have observed that the disparate scale nonlinear interactions between the high-frequency (∼0.4 MHz) electron temperature gradient (ETG) mode and the ion-scale low-frequency fluctuations (∼kHz) were enhanced when the amplitude of the ETG mode exceeded a certain threshold. The dynamics of nonlinear coupling between the ETG mode and the drift wave (DW) mode has already been reported [C. Moon, T. Kaneko, and R. Hatakeyama, Phys. Rev. Lett. (2013)]. Here, we have newly observed that another low-frequency fluctuation with f ≃ 3.6 kHz, i.e., the flute mode, was enhanced, corresponding to the saturation of the DW mode growth. Specifically, the bicoherence between the flute mode and the DW mode reaches a significant level when the ∇T{sub e}/T{sub e} strength exceeded 0.54 cm{sup −1}. Thus, it is shown that the ETG mode energy was transferred to the DW mode, and then the energy was ultimately transferred to the flute mode, which was triggered by the disparate scale nonlinear interactions between the ETG and ion-scale low-frequency modes.
Colloquium: Nonlinear collective interactions in quantum plasmas with degenerate electron fluids
Shukla, P. K.; Eliasson, B.
2011-07-01
The current understanding of some important nonlinear collective processes in quantum plasmas with degenerate electrons is presented. After reviewing the basic properties of quantum plasmas, model equations (e.g., the quantum hydrodynamic and effective nonlinear Schroedinger-Poisson equations) are presented that describe collective nonlinear phenomena at nanoscales. The effects of the electron degeneracy arise due to Heisenberg's uncertainty principle and Pauli's exclusion principle for overlapping electron wave functions that result in tunneling of electrons and the electron degeneracy pressure. Since electrons are Fermions (spin-1/2 quantum particles), there also appears an electron spin current and a spin force acting on electrons due to the Bohr magnetization. The quantum effects produce new aspects of electrostatic (ES) and electromagnetic (EM) waves in a quantum plasma that are summarized in here. Furthermore, nonlinear features of ES ion waves and electron plasma oscillations are discussed, as well as the trapping of intense EM waves in quantum electron-density cavities. Specifically, simulation studies of the coupled nonlinear Schroedinger and Poisson equations reveal the formation and dynamics of localized ES structures at nanoscales in a quantum plasma. The effect of an external magnetic field on the plasma wave spectra and develop quantum magnetohydrodynamic equations are also discussed. The results are useful for understanding numerous collective phenomena in quantum plasmas, such as those in compact astrophysical objects (e.g., the cores of white dwarf stars and giant planets), as well as in plasma-assisted nanotechnology (e.g., quantum diodes, quantum free-electron lasers, nanophotonics and nanoplasmonics, metallic nanostructures, thin metal films, semiconductor quantum wells, and quantum dots, etc.), and in the next generation of intense laser-solid density plasma interaction experiments relevant for fast ignition in inertial confinement fusion
NASA Technical Reports Server (NTRS)
Kim, H.; Crawford, F. W.
1977-01-01
It is pointed out that the conventional iterative analysis of nonlinear plasma wave phenomena, which involves a direct use of Maxwell's equations and the equations describing the particle dynamics, leads to formidable theoretical and algebraic complexities, especially for warm plasmas. As an effective alternative, the Lagrangian method may be applied. It is shown how this method may be used in the microscopic description of small-signal wave propagation and in the study of nonlinear wave interactions. The linear theory is developed for an infinite, homogeneous, collisionless, warm magnetoplasma. A summary is presented of a perturbation expansion scheme described by Galloway and Kim (1971), and Lagrangians to third order in perturbation are considered. Attention is given to the averaged-Lagrangian density, the action-transfer and coupled-mode equations, and the general solution of the coupled-mode equations.
Non-linear wave interaction in a magnetoplasma column. I - Theory. II Experiment
NASA Technical Reports Server (NTRS)
Larsen, J.-M.; Crawford, F. W.
1979-01-01
The paper presents an analysis of non-linear three-wave interaction for propagation along a cylindrical plasma column surrounded either by a metallic boundary, or by an infinite dielectric, and immersed in an infinite, static, axial magnetic field. An averaged Lagrangian method is used and the results are specialized to parametric amplification and mode conversion, assuming an undepleted pump wave. Computations are presented for a magneto-plasma column surrounded by free space, indicating that parametric growth rates of the order of a fraction of a decibel per centimeter should be obtainable for plausible laboratory plasma parameters. In addition, experiments on non-linear mode conversion in a cylindrical magnetoplasma column are described. The results are compared with the theoretical predictions and good qualitative agreement is demonstrated.
Khorashadizadeh, S. M. Taheri Boroujeni, S.; Niknam, A. R.
2015-11-15
In this paper, we have investigated the nonlinear interaction between high-frequency surface plasmons and low-frequency ion oscillations in a semi-bounded collisional quantum plasma. By coupling the nonlinear Schrodinger equation and quantum hydrodynamic model, and taking into account the ponderomotive force, the dispersion equation is obtained. By solving this equation, it is shown that there is a modulational instability in the system, and collisions and quantum forces play significant roles on this instability. The quantum tunneling increases the phase and group velocities of the modulated waves and collisions increase the growth rate of the modulational instability. It is also shown that the effect of quantum forces and collisions is more significant in high modulated wavenumber regions.
On Nonlinear Self-interaction of Geodesic Acoustic Mode Driven by Energetic Particles
G. Y. Fu
2010-06-04
It is shown that nonlinear self-interaction of energetic particle-driven Geodesic Acoustic Mode does not generate a second harmonic in radial electric field using the fluid model. However, kinetic effects of energetic particles can induce a second harmonic in the radial electric field. A formula for the second order plasma density perturbation is derived. It is shown that a second harmonic of plasma density perturbation is generated by the convective nonlinearity of both thermal plasma and energetic particles. Near the midplane of a tokamak, the second order plasma density perturbation (the sum of second harmonic and zero frequency sideband) is negative on the low field side with its size comparable to the main harmonic at low uctuation level. These analytic predictions are consistent with the recent experimental observation in DIII-D.
On Nonlinear Self-interaction of Geodesic Acoustic Mode Driven By Energetic Particles
G.Y. Fu
2010-10-01
It is shown that nonlinear self-interaction of energetic particle-driven Geodesic Acoustic Mode does not generate a second harmonic in radial electric field using the fluid model. However, kinetic effects of energetic particles can induce a second harmonic in the radial electric field. A formula for the second order plasma density perturbation is derived. It is shown that a second harmonic of plasma density perturbation is generated by the convective nonlinearity of both thermal plasma and energetic particles. Near the midplane of a tokamak, the second order plasma density perturbation (the sum of second harmonic and zero frequency sideband) is negative on the low field side with its size comparable to the main harmonic at low fluctuation level. These analytic predictions are consistent with the recent experimental observation in DIII-D.
Dual roles of shear flow in nonlinear multi-scale interactions
NASA Astrophysics Data System (ADS)
Hu, Z. Q.; Wang, Z. X.; Wei, L.; Li, J. Q.; Kishimoto, Y.
2016-01-01
Effect of shear flow on the multi-scale nonlinear interaction in plasmas is numerically investigated by using a self-consistent Landau-fluid model. Dual roles of shear flow in the process are discovered, significantly suppressing micro-scale fluctuations and dramatically promoting macro-scale fluctuations. Furthermore, its similar dual roles in turbulent transport are also demonstrated. The novel underlying mechanism for the nonlinear promotion is identified as the formation of a large vortex flow inside magnetic island, which as a common phenomenon have been often observed in space and magnetic fusion plasmas. The theoretical prediction on the threshold of shear flow based on an analytical modeling is verified via numerical simulations.
NASA Astrophysics Data System (ADS)
Zhai, Shidong
2016-04-01
This paper studies the collective behavior in a network of nonlinear systems with antagonistic interactions and switching topologies. The concept of modulus synchronization is introduced to characterize the case that the moduli of corresponding components of the agent (node) states reach a synchronization. The network topologies are modeled by a set of directed signed graphs. When all directed signed graphs are structurally balanced and the nonlinear system satisfies a one-sided Lipschitz condition, by using matrix measure and contraction theory, we show that modulus synchronization can be evaluated by the time average of some matrix measures. These matrices are about the second smallest eigenvalue of undirected graphs corresponding to directed signed graphs. Finally, we present two numerical examples to illustrate the effectiveness of the obtained results.
A bundled-stack discotic columnar liquid crystalline phase with inter-stack electronic coupling
Wang, Bin; Sun, Runkun; Günbaş, Duygu D.; Zhang, Hao; Grozema, Ferdinand C.; Xiao, Kai; Jin, Shi
2015-06-15
The first compound proving to be capable of forming a bundled-stack discotic columnar liquid crystalline (BSDCLC) phase was designed and synthesized. Finally, the unique perylene anhydride inter-stack interaction was found to be the key to the formation of the BSDCLC structure and inter-stack electronic coupling (ISEC).
Bundled Stack Discotic Columnar Liquid Crystalline Phase with Inter Stack Electronic Coupling
Wang, Bin; Sun, Runkun; Gunbas, Duygu; Zhang, Hao; Grozema, Ferdinand; Xiao, Kai; Jin, Shi
2015-01-01
The first compound capable of forming a bundled stack discotic columnar liquid crystalline (BSDCLC) phase was designed and synthesized. The unique perylene anhydride inter stack interaction was found to be the key to the formation of the BSDCLC structure and inter stack electronic coupling (ISEC).
Goldin, Matías A.; Alonso, Leandro M.; Alliende, Jorge A.; Goller, Franz; Mindlin, Gabriel B.
2013-01-01
The nature of telencephalic control over premotor and motor circuits is debated. Hypotheses range from complete usurping of downstream circuitry to highly interactive mechanisms of control. We show theoretically and experimentally, that telencephalic song motor control in canaries is consistent with a highly interactive strategy. As predicted from a theoretical model of respiratory control, mild cooling of a forebrain nucleus (HVC) led to song stretching, but further cooling caused progressive restructuring of song, consistent with the hypothesis that respiratory gestures are subharmonic responses to a timescale present in the output of HVC. This interaction between a life-sustaining motor function (respiration) and telencephalic song motor control suggests a more general mechanism of how nonlinear integration of evolutionarily new brain structures into existing circuitry gives rise to diverse, new behavior. PMID:23818988
Nonlinear wave interactions between short pulses of different spatio-temporal extents
Sivan, Y.; Rozenberg, S.; Halstuch, A.; Ishaaya, A. A.
2016-01-01
We study the nonlinear wave interactions between short pulses of different spatio-temporal extents. Unlike the well-understood mixing of quasi-monochromatic waves, this configuration is highly non-intuitive due to the complex coupling between the spatial and temporal degrees of freedom of the interacting pulses. We illustrate the process intuitively with transitions between different branches of the dispersion curves and interpret it in terms of spectral exchange between the interacting pulses. We verify our interpretation with an example whereby a spectrally-narrow pulse “inherits” the wide spectrum of a pump pulse centered at a different wavelength, using exact numerical simulations, as well as a simplified coupled mode analysis and an asymptotic analytical solution. The latter also provides a simple and intuitive quantitative interpretation. The complex wave mixing process studied here may enable flexible spatio-temporal shaping of short pulses and is the starting point of the study of more complicated systems. PMID:27381552
Wu, Y.; Xu, Z.; Li, Z. H.; Tang, C. X.
2012-07-15
In intermediate cavities of a relativistic klystron amplifier (RKA) driven by intense relativistic electron beam, the equivalent circuit model, which is widely adopted to investigate the interaction between bunched beam and the intermediate cavity in a conventional klystron design, is invalid due to the high gap voltage and the nonlinear beam loading in a RKA. According to Maxwell equations and Lorentz equation, the self-consistent equations for beam-wave interaction in the intermediate cavity are introduced to study the nonlinear interaction between bunched beam and the intermediate cavity in a RKA. Based on the equations, the effects of modulation depth and modulation frequency of the beam on the gap voltage amplitude and its phase are obtained. It is shown that the gap voltage is significantly lower than that estimated by the equivalent circuit model when the beam modulation is high. And the bandwidth becomes wider as the beam modulation depth increases. An S-band high gain relativistic klystron amplifier is designed based on the result. And the corresponding experiment is carried out on the linear transformer driver accelerator. The peak output power has achieved 1.2 GW with an efficiency of 28.6% and a gain of 46 dB in the corresponding experiment.
Nonlinear Interaction of the Beat-Photon Beams with the Brain Neurocenters: Laser Neurophysics
NASA Astrophysics Data System (ADS)
Stefan, V. Alexander
2010-03-01
I propose a novel mechanism for laser-brain interaction: Nonlinear interaction of ultrashort pulses of beat-photon, (φ1-- φ2), or double-photon, (φ1+φ2), footnotetextMaria Goeppert-Mayer, "Uber Elementarakte mit zwei Quantenspr"ungen, Ann Phys 9, 273, 95. (1931). beams with the corrupted brain neurocenters, causing a particular neurological disease. The open-scull cerebral tissue can be irradiated with the beat-photon pulses in the range of several 100s fs, with the laser irradiances in the range of a few mW/cm^2, repetition rate of a few 100s Hz, and in the frequency range of 700-1300nm generated in the beat-wave driven free electron laser.footnotetextV. Alexander Stefan, The Interaction of Photon Beams with the DNA Molecules: Genomic Medical Physics. American Physical Society, 2009 APS March Meeting, March 16-20, 2009, abstract #K1.276; V. Stefan, B. I. Cohen, and C. Joshi, Nonlinear Mixing of Electromagnetic Waves in Plasmas Science 27 January 1989:Vol. 243. no. 4890, pp. 494 -- 500 (January 1989). This method may prove to be an effective mechanism in the treatment of neurological diseases: Parkinson's, Lou Gehrig's, and others.
Itasse, Maxime Brazier, Jean-Philippe Léon, Olivier Casalis, Grégoire
2015-08-15
Nonlinear evolution of disturbances in an axisymmetric, high subsonic, high Reynolds number hot jet with forced eigenmodes is studied using the Parabolized Stability Equations (PSE) approach to understand how modes interact with one another. Both frequency and azimuthal harmonic interactions are analyzed by setting up one or two modes at higher initial amplitudes and various phases. While single mode excitation leads to harmonic growth and jet noise amplification, controlling the evolution of a specific mode has been made possible by forcing two modes (m{sub 1}, n{sub 1}), (m{sub 2}, n{sub 2}), such that the difference in azimuth and in frequency matches the desired “target” mode (m{sub 1} − m{sub 2}, n{sub 1} − n{sub 2}). A careful setup of the initial amplitudes and phases of the forced modes, defined as the “killer” modes, has allowed the minimizing of the initially dominant instability in the near pressure field, as well as its estimated radiated noise with a 15 dB loss. Although an increase of the overall sound pressure has been found in the range of azimuth and frequency analyzed, the present paper reveals the possibility to make the initially dominant instability ineffective acoustically using nonlinear interactions with forced eigenmodes.
On nonlinear Tollmien-Schlichting/vortex interaction in three-dimensional boundary layers
NASA Technical Reports Server (NTRS)
Davis, Dominic A. R.; Smith, Frank T.
1993-01-01
The instability of an incompressible three-dimensional boundary layer (that is, one with cross-flow) is considered theoretically and computationally in the context of vortex/wave interactions. Specifically the work centers on two low amplitude, lower-branch Tollmien-Schlichting waves which mutually interact to induce a weak longitudinal vortex flow; the vortex motion, in turn, gives rise to significant wave-modulation via wall-shear forcing. The characteristic Reynolds number is taken as a large parameter and, as a consequence, the waves' and the vortex motion are governed primarily by triple-deck theory. The nonlinear interaction is captured by a viscous partial-differential system for the vortex coupled with a pair of amplitude equations for each wave pressure. Three distinct possibilities were found to emerge for the nonlinear behavior of the flow solution downstream - an algebraic finite-distance singularity, far downstream saturation or far-downstream wave-decay (leaving pure vortex flow) - depending on the input conditions, the wave angles, and the size of the cross-flow.
Global Spiral Arms Formation by Non-linear Interaction of Wakelets
NASA Astrophysics Data System (ADS)
Kumamoto, Jun; Noguchi, Masafumi
2016-05-01
The formation and evolution of galactic spiral arms is not yet clearly understood despite much analytic and numerical work. Recently, the new idea has been proposed that local density enhancements (wakelets) arising in the galactic disk connect with each other and make global spiral arms. However, the understanding of this mechanism is not yet sufficient. We analyze the interaction of wakelets by using N-body simulations, including perturbing point masses, which are heavier than individual N-body particles and act as the seeds for wakelets. Our simulation facilitates a more straightforward interpretation of numerical results than previous works by putting a certain number of perturbers in a well-motivated configuration. We detected a clear sign of non-linear interaction between wakelets, which make global spiral arms by connecting two adjacent wakelets. We found that the wavenumber of the strongest non-linear interaction depends on galactic disk mass and shear rate. This dependence is consistent with the prediction of a swing amplification mechanism and other previous results. Our results unify previous results that were consistent with each other.
Weak ENSO asymmetry due to weak nonlinear air-sea interaction in CMIP5 climate models
NASA Astrophysics Data System (ADS)
Sun, Yan; Wang, Fan; Sun, De-Zheng
2016-03-01
State-of-the-art climate models have long-standing intrinsic biases that limit their simulation and projection capabilities. Significantly weak ENSO asymmetry and weakly nonlinear air-sea interaction over the tropical Pacific was found in CMIP5 (Coupled Model Intercomparison Project, Phase 5) climate models compared with observation. The results suggest that a weak nonlinear air-sea interaction may play a role in the weak ENSO asymmetry. Moreover, a weak nonlinearity in air-sea interaction in the models may be associated with the biases in the mean climate—the cold biases in the equatorial central Pacific. The excessive cold tongue bias pushes the deep convection far west to the western Pacific warm pool region and suppresses its development in the central equatorial Pacific. The deep convection has difficulties in further moving to the eastern equatorial Pacific, especially during extreme El Ni˜no events, which confines the westerly wind anomaly to the western Pacific. This weakens the eastern Pacific El Ni˜no events, especially the extreme El Ni˜no events, and thus leads to the weakened ENSO asymmetry in climate models. An accurate mean state structure (especially a realistic cold tongue and deep convection) is critical to reproducing ENSO events in climate models. Our evaluation also revealed that ENSO statistics in CMIP5 climate models are slightly improved compared with those of CMIP3. The weak ENSO asymmetry in CMIP5 is closer to the observation. It is more evident in CMIP5 that strong ENSO activities are usually accompanied by strong ENSO asymmetry, and the diversity of ENSO amplitude is reduced.
Evidence of nonlinear interaction between quasi 2 day wave and quasi-stationary wave
NASA Astrophysics Data System (ADS)
Gu, Sheng-Yang; Liu, Han-Li; Li, Tao; Dou, Xiankang; Wu, Qian; Russell, James M.
2015-02-01
The nonlinear interaction between the westward quasi 2 day wave (QTDW) with zonal wave number s = 3 (W3) and stationary planetary wave with s = 1 (SPW1) is first investigated using both Thermosphere, Ionosphere, and Mesosphere Electric Dynamics (TIMED) satellite observations and the thermosphere-ionosphere-mesosphere electrodynamics general circulation model (TIME-GCM) simulations. A QTDW with westward s = 2 (W2) is identified in the mesosphere and lower thermosphere (MLT) region in TIMED/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature and TIMED/TIMED Doppler Imager (TIDI) wind observations during 2011/2012 austral summer period, which coincides with a strong SPW1 episode at high latitude of the northern winter hemisphere. The temperature perturbation of W2 QTDW reaches a maximum amplitude of ~8 K at ~30°S and ~88 km in the Southern Hemisphere, with a smaller amplitude in the Northern Hemisphere at similar latitude and minimum amplitude at the equator. The maximum meridional wind amplitude of the W2 QTDW is observed to be ~40 m/s at 95 km in the equatorial region. The TIME-GCM is utilized to simulate the nonlinear interactions between W3 QTDW and SPW1 by specifying both W3 QTDW and SPW1 perturbations at the lower model boundary. The model results show a clear W2 QTDW signature in the MLT region, which agrees well with the TIMED/SABER temperature and TIMED/TIDI horizontal wind observations. We conclude that the W2 QTDW during the 2011/2012 austral summer period results from the nonlinear interaction between W3 QTDW and SPW1.
NASA Technical Reports Server (NTRS)
Tang, H. T.; Hofmann, R.; Yee, G.; Vaughan, D. K.
1980-01-01
Transient, nonlinear soil-structure interaction simulations of an Electric Power Research Institute, SIMQUAKE experiment were performed using the large strain, time domain STEALTH 2D code and a cyclic, kinematically hardening cap soil model. Results from the STEALTH simulations were compared to identical simulations performed with the TRANAL code and indicate relatively good agreement between all the STEALTH and TRANAL calculations. The differences that are seen can probably be attributed to: (1) large (STEALTH) vs. small (TRANAL) strain formulation and/or (2) grid discretization differences.
NASA Astrophysics Data System (ADS)
Dai, Zhiping; Yang, Zhenjun; Ling, Xiaohui; Zhang, Shumin; Pang, Zhaoguang; Li, Jianxing
2016-05-01
The motion of two interactional solitons is investigated in nonlinear media with an exponential nonlocal response. A differential equation describing the motion trajectories of soliton center is proposed. Some numerical simulations are performed to illustrate the characteristics of the motion trajectories. The results show that the trajectories always oscillate periodically. However, if the two solitons are launched with a relative inclined angle which is larger than a critical value, they do not collide any more but diverge from each other. The critical angle is also given.
An accelerated method of computing nonlinear processes in instruments with longitudinal interaction
NASA Astrophysics Data System (ADS)
Pikunov, V. M.; Prokopev, V. E.; Sandalov, A. N.
1985-04-01
The use of the reference particle method for investigating nonlinear processes in instruments with longitudinal interaction is considered in an attempt to accelerate the computation of the processes. It is demonstrated that, coupled with interpolation formulas based on Kotelnikov series, the method yields effective numerical algorithms in the framework of discrete models of electron flux. A comparison of the method with a disk model of an electron flux for the case of multiresonator clistron was performed for clistron bunchers with 50 to 80-percent efficiency. It is concluded that the computation time was reduced by a factor of 3-10 while maintaining satisfactory accuracy.
Recent Progress on Nonlinear Schrödinger Systems with Quadratic Interactions
Li, Chunhua; Hayashi, Nakao
2014-01-01
The study of nonlinear Schrödinger systems with quadratic interactions has attracted much attention in the recent years. In this paper, we summarize time decay estimates of small solutions to the systems under the mass resonance condition in 2-dimensional space. We show the existence of wave operators and modified wave operators of the systems under some mass conditions in n-dimensional space, where n ≥ 2. The existence of scattering operators and finite time blow-up of the solutions for the systems in higher space dimensions is also shown. PMID:25143965
Multiphysics modeling of non-linear laser-matter interactions for optically active semiconductors
NASA Astrophysics Data System (ADS)
Kraczek, Brent; Kanp, Jaroslaw
Development of photonic devices for sensors and communications devices has been significantly enhanced by computational modeling. We present a new computational method for modelling laser propagation in optically-active semiconductors within the paraxial wave approximation (PWA). Light propagation is modeled using the Streamline-upwind/Petrov-Galerkin finite element method (FEM). Material response enters through the non-linear polarization, which serves as the right-hand side of the FEM calculation. Maxwell's equations for classical light propagation within the PWA can be written solely in terms of the electric field, producing a wave equation that is a form of the advection-diffusion-reaction equations (ADREs). This allows adaptation of the computational machinery developed for solving ADREs in fluid dynamics to light-propagation modeling. The non-linear polarization is incorporated using a flexible framework to enable the use of multiple methods for carrier-carrier interactions (e.g. relaxation-time-based or Monte Carlo) to enter through the non-linear polarization, as appropriate to the material type. We demonstrate using a simple carrier-carrier model approximating the response of GaN. Supported by ARL Materials Enterprise.
Three-photon interactions and spin exchange in a quantum nonlinear medium
NASA Astrophysics Data System (ADS)
Cantu, Sergio; Liang, Qi-Yu; Thompson, Jeff; Nicholson, Travis; Venkatramani, Aditya; Gullans, Michael; Gorshkov, Alexey; Choi, Soonwon; Lukin, Mikhail; Vuletic, Vladan
2016-05-01
Robust quantum gates for photonic qubits are a longstanding goal of quantum information science. One promising approach to achieve this goal requires strong nonlinear interactions between single photons, which is impossible with conventional optical media. We realize these interactions with electromagnetically induced transparency (EIT), and strongly interacting Rydberg states to mediate strong interactions between photons. Operating in the dispersive regime of EIT, we have recently shown that two photons propagating in our system can bind into a photonic molecule. Extending these two-photon experiments to many-body physics would lead to exotic phenomena like photon crystallization. To that end, we have scaled up our two-photon measurements to three-photon experiments. We are now able to discern signatures of three-photon molecules from a variety of two- and three-photon interactions. Three-photon bound states manifest as an increase in photon bunching in g (3) correlation measurements. We also present a recent observation of coherent spin exchange interactions in Rydberg EIT.
Lee, Seunghak; Lozano, Aurélie; Kambadur, Prabhanjan; Xing, Eric P
2016-05-01
Genome-wide association studies have revealed individual genetic variants associated with phenotypic traits such as disease risk and gene expressions. However, detecting pairwise interaction effects of genetic variants on traits still remains a challenge due to a large number of combinations of variants (∼10(11) SNP pairs in the human genome), and relatively small sample sizes (typically <10(4)). Despite recent breakthroughs in detecting interaction effects, there are still several open problems, including: (1) how to quickly process a large number of SNP pairs, (2) how to distinguish between true signals and SNPs/SNP pairs merely correlated with true signals, (3) how to detect nonlinear associations between SNP pairs and traits given small sample sizes, and (4) how to control false positives. In this article, we present a unified framework, called SPHINX, which addresses the aforementioned challenges. We first propose a piecewise linear model for interaction detection, because it is simple enough to estimate model parameters given small sample sizes but complex enough to capture nonlinear interaction effects. Then, based on the piecewise linear model, we introduce randomized group lasso under stability selection, and a screening algorithm to address the statistical and computational challenges mentioned above. In our experiments, we first demonstrate that SPHINX achieves better power than existing methods for interaction detection under false positive control. We further applied SPHINX to late-onset Alzheimer's disease dataset, and report 16 SNPs and 17 SNP pairs associated with gene traits. We also present a highly scalable implementation of our screening algorithm, which can screen ∼118 billion candidates of associations on a 60-node cluster in <5.5 hours. PMID:27159633
Nonlinear Dynamics of Cantilever-Sample Interactions in Atomic Force Microscopy
NASA Technical Reports Server (NTRS)
Cantrell, John H.; Cantrell, Sean A.
2010-01-01
The interaction of the cantilever tip of an atomic force microscope (AFM) with the sample surface is obtained by treating the cantilever and sample as independent systems coupled by a nonlinear force acting between the cantilever tip and a volume element of the sample surface. The volume element is subjected to a restoring force from the remainder of the sample that provides dynamical equilibrium for the combined systems. The model accounts for the positions on the cantilever of the cantilever tip, laser probe, and excitation force (if any) via a basis set of set of orthogonal functions that may be generalized to account for arbitrary cantilever shapes. The basis set is extended to include nonlinear cantilever modes. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a matrix iteration procedure. The effects of oscillatory excitation forces applied either to the cantilever or to the sample surface (or to both) are obtained from the solution set and applied to the to the assessment of phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) modalities. The influence of bistable cantilever modes of on AFM signal generation is discussed. The effects on the cantilever-sample surface dynamics of subsurface features embedded in the sample that are perturbed by surface-generated oscillatory excitation forces and carried to the cantilever via wave propagation are accounted by the Bolef-Miller propagating wave model. Expressions pertaining to signal generation and image contrast in A-AFM are obtained and applied to amplitude modulation (intermittent contact) atomic force microscopy and resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM). The influence of phase accumulation in A-AFM on image contrast is discussed, as is the effect of hard contact and maximum nonlinearity regimes of A-AFM operation.
Nonlinear multiple-discipline analysis of conjugate heat transfer and fluid-structure interaction
NASA Astrophysics Data System (ADS)
Weaver, Michael A.
Single-discipline analysis approaches often utilize linearized descriptions of coupled system physics from other disciplines. When this level of approximation is inadequate for the purposes of the analysis, nonlinear governing equations for the separate physical disciplines must be introduced, thus producing a multiple-discipline analysis. The multiple-discipline approach can provide a deeper understanding of the underlying system physics, and can reveal deficiencies in systems designed by single-discipline means. An advantageous way to examine a nonlinear multiple-discipline system is the partitioned method, where each discipline subdomain is formulated and discretized separately, allowing separate modular solvers for each set of discretized equations. Avoiding ad hoc approaches, a unified approach is developed here and applied to analysis of conjugate heat transfer in an arc-heater wind tunnel nozzle, and fluid-structure interaction of a segmented solid rocket motor inhibitor. The specific systems examined represent actual hardware designed by single-discipline methods. The nonlinear effects present in the wind tunnel nozzle problem include separated, viscous fluid flow, forced-convection boiling, and flow-dependent heat transfer properties. Nonlinear effects present in the solid rocket motor inhibitor problem include large structural deformation, and separated, viscous fluid flow. Steady-state results obtained for the nozzle problem show distributions for wall temperature, fluid temperatures, and heat flux, as well as coolant flow field and recirculation patterns. These results indicate a design deficiency in the nozzle cooling system. For the inhibitor problem, steady and unsteady fields of stress, strain, and displacement are obtained for the structural components, accompanied by velocity and pressure fields for the surrounding gas flow. The large stress values present in the solid propellant suggest a possible mode for motor failure, and beckon examination of
Li, Qian; Wang, Jing; Zheng, Yuqing Yuan; Yang, Lingjian; Zhang, Yajun; Bian, Liujiao; Zheng, Jianbin; Li, Zijian; Zhao, Xinfeng; Zhang, Youyi
2015-07-01
Zonal elution and nonlinear chromatography are two mainstream models for the determination of drug-protein interaction in affinity chromatography. This work intended to compare the results by zonal elution with that by nonlinear chromatography when it comes to the analysis of the interaction between seven drugs and immobilised β2-adrenoceptor (β2-AR). The results of the zonal elution showed that clorprenaline, clenbuterol, methoxyphenamine, salbutamol, terbutaline, tulobuterol and bambuterol have only one type of binding site on immobilised β2-AR, while nonlinear chromatography confirmed the existence of at least two types of binding sites between β2-AR and clorprenaline, clenbuterol and bambuterol. On these sites, both zonal elution and nonlinear chromatography presented the same rank order for the association constants of the seven drugs. Compared with the data from zonal elution, the association constants calculated using nonlinear chromatography gave a good linear response to the corresponding values by radio-ligand binding assay. The sampling efficiencies of nonlinear chromatography were clearly higher than zonal elution. Nonlinear chromatography will probably become a powerful alternative for the high throughput determination of drug-protein interaction. PMID:26002106
Electrochemical cell stack assembly
Jacobson, Craig P.; Visco, Steven J.; De Jonghe, Lutgard C.
2010-06-22
Multiple stacks of tubular electrochemical cells having a dense electrolyte disposed between an anode and a cathode preferably deposited as thin films arranged in parallel on stamped conductive interconnect sheets or ferrules. The stack allows one or more electrochemical cell to malfunction without disabling the entire stack. Stack efficiency is enhanced through simplified gas manifolding, gas recycling, reduced operating temperature and improved heat distribution.
Interactive application of quadratic expansion of chi-square statistic to nonlinear curve fitting
NASA Technical Reports Server (NTRS)
Badavi, F. F.; Everhart, Joel L.
1987-01-01
This report contains a detailed theoretical description of an all-purpose, interactive curve-fitting routine that is based on P. R. Bevington's description of the quadratic expansion of the Chi-Square statistic. The method is implemented in the associated interactive, graphics-based computer program. Taylor's expansion of Chi-Square is first introduced, and justifications for retaining only the first term are presented. From the expansion, a set of n simultaneous linear equations is derived, then solved by matrix algebra. A brief description of the code is presented along with a limited number of changes that are required to customize the program of a particular task. To evaluate the performance of the method and the goodness of nonlinear curve fitting, two typical engineering problems are examined and the graphical and tabular output of each is discussed. A complete listing of the entire package is included as an appendix.
Proposal of a Nonlinear Interaction of Person and Situation (NIPS) model
Schmitt, Manfred; Gollwitzer, Mario; Baumert, Anna; Blum, Gabriela; Gschwendner, Tobias; Hofmann, Wilhelm; Rothmund, Tobias
2013-01-01
Marshall and Brown (2006) proposed a Traits as Situational Sensitivities (TASS) Model, which implies a systematic person × situation interaction. We review this model and show that it suffers from several limitations. We extend and modify the model in order to obtain a symmetric pattern of levels and effects for both person and situation factors. Our suggestions result in a general Nonlinear Interaction of Person and Situation (NIPS) Model. The NIPS model bears striking similarities to the Rasch model. Based on the symmetric nature of the NIPS model, we generalize the concept of weak and strong situations to individuals and propose the concepts of weak and strong persons. Finally, we discuss psychological mechanisms that might explain the NIPS pattern and offer ideas for future research. PMID:23935588
NASA Astrophysics Data System (ADS)
Zhang, Qingling
2016-03-01
This paper is devoted to studying the simplified nonlinear chromatography equations by introducing the change of state variables. The Riemann solutions containing delta shock waves are presented. In order to study wave interactions of delta shock waves with elementary waves, the global structure of solutions is constructed completely when the initial data are taken as three pieces of constants and the delta shock waves are included. In particular, the strength of delta shock wave is expressed explicitly and the delta contact discontinuity is discovered during the process of wave interactions. Moreover, by analyzing the limits of the solutions as the middle region vanishes, we observe that the Riemann solutions are stable for such a local small perturbation of the Riemann initial data.
Nonlinear dynamic response of a simple ice-structure interaction model
Karr, D.G.; Troesch, A.W.; Wingate, W.C. . Dept. of Naval Architecture and Marine Engineering)
1993-11-01
The problem addressed in the continuous indentation of a ship or offshore structure into an ice sheet. The impacting ship or offshore structure is represented by a mass-spring-dashpot system having a constant velocity relative to the ice sheet. The dynamic response of this simple analogue model of ice-structure interaction is studied in considerable detail. The complicated, highly nonlinear dynamic response is due to intermittent ice breakage and intermittent contact of the structure with the ice. Periodic motions are found and the periodicity for a particular system is dependent upon initial conditions. For a representative system, a Poincare map is presented showing the fixed points. A description of some of the effects of random variations in system parameters is also presented. Some implications of these findings regarding structural design for ice interaction are discussed.
Moore, Jason H
2010-01-01
Human health is a complex process that is dependent on many genes, many environmental factors and chance events that are perhaps not measurable with current technology or are simply unknowable. Success in the design and execution of population-based association studies to identify those genetic and environmental factors that play an important role in human disease will depend on our ability to embrace, rather that ignore, complexity in the genotype to phenotype mapping relationship for any given human ecology. We review here three general computational challenges that must be addressed. First, data mining and machine learning methods are needed to model nonlinear interactions between multiple genetic and environmental factors. Second, filter and wrapper methods are needed to identify attribute interactions in large and complex solution landscapes. Third, visualization methods are needed to help interpret computational models and results. We provide here an overview of the multifactor dimensionality reduction (MDR) method that was developed for addressing each of these challenges. PMID:21029850
NASA Astrophysics Data System (ADS)
Wang, Lei; Zhang, Jian-Hui; Wang, Zi-Qi; Liu, Chong; Li, Min; Qi, Feng-Hua; Guo, Rui
2016-01-01
We study the nonlinear waves on constant backgrounds of the higher-order generalized nonlinear Schrödinger (HGNLS) equation describing the propagation of ultrashort optical pulse in optical fibers. We derive the breather, rogue wave, and semirational solutions of the HGNLS equation. Our results show that these three types of solutions can be converted into the nonpulsating soliton solutions. In particular, we present the explicit conditions for the transitions between breathers and solitons with different structures. Further, we investigate the characteristics of the collisions between the soliton and breathers. Especially, based on the semirational solutions of the HGNLS equation, we display the novel interactions between the rogue waves and other nonlinear waves. In addition, we reveal the explicit relation between the transition and the distribution characteristics of the modulation instability growth rate.
Wang, Lei; Zhang, Jian-Hui; Wang, Zi-Qi; Liu, Chong; Li, Min; Qi, Feng-Hua; Guo, Rui
2016-01-01
We study the nonlinear waves on constant backgrounds of the higher-order generalized nonlinear Schrödinger (HGNLS) equation describing the propagation of ultrashort optical pulse in optical fibers. We derive the breather, rogue wave, and semirational solutions of the HGNLS equation. Our results show that these three types of solutions can be converted into the nonpulsating soliton solutions. In particular, we present the explicit conditions for the transitions between breathers and solitons with different structures. Further, we investigate the characteristics of the collisions between the soliton and breathers. Especially, based on the semirational solutions of the HGNLS equation, we display the novel interactions between the rogue waves and other nonlinear waves. In addition, we reveal the explicit relation between the transition and the distribution characteristics of the modulation instability growth rate. PMID:26871080
The nonlinear interaction of two-crossed focussed ultrasonic beams in the presence of turbulence
NASA Astrophysics Data System (ADS)
Rife, Stephen C.
1988-06-01
This paper examines the scattering of a nonlinearly generated sum frequency acoustic wave component from a region of turbulence defined by the overlap volume of two mutually perpendicular crossed focussed ultrasonic beams. The scattered sum frequency pressure amplitude is measured at different radial scan positions across the jet flow stream providing conclusions that explain some qualitative results governing the sum frequency scattering mechanism. Information about the instantaneous velocity components of the turbulent field in the sound-sound interaction volume is measured with an electronic spectrum analyzer. Average spectral shapes of the spectrum near the sum frequency represent information about the probability distribution function of the turbulent velocities. Acoustic measurements are correlated with velocity measurements of circular jets. These correlations demonstrate that the focussed crossed beam apparatus is an effective diagnostic tool for the experimental study of turbulent fluid fields in water. The results of the nonlinear crossed beam experiments indicate the apparatus can be utilized as a diagnostic tool to measure some parameters of turbulent velocity. The measured pressure of the radiated sum frequency correlates with turbulent velocities in the interaction region. Measurements of the Doppler shift and sum-frequency broadening are used to determine mean velocity and turbulent rms velocities respectively.
Nonlinear Interaction of Detuned Instability Waves in Boundary-Layer Transition: Amplitude Equations
NASA Technical Reports Server (NTRS)
Lee, Sang Soo
1998-01-01
The non-equilibrium critical-layer analysis of a system of frequency-detuned resonant-triads is presented. In this part of the analysis, the system of partial differential critical-layer equations derived in Part I is solved analytically to yield the amplitude equations which are analyzed using a combination of asymptotic and numerical methods. Numerical solutions of the inviscid non-equilibrium oblique-mode amplitude equations show that the frequency-detuned self-interaction enhances the growth of the lower-frequency oblique modes more than the higher-frequency ones. All amplitudes become singular at the same finite downstream position. The frequency detuning delays the occurrence of the singularity. The spanwise-periodic mean-flow distortion and low-frequency nonlinear modes are generated by the critical-layer interaction between frequency-detuned oblique modes. The nonlinear mean flow and higher harmonics as well as the primary instabilities become as large as the base mean flow in the inviscid wall layer in the downstream region where the distance from the singularity is of the order of the wavelength scale.
Nonlinear interaction of a fast magnetogasdynamic shock with a tangential discontinuity
NASA Technical Reports Server (NTRS)
Neubauer, F. M.
1973-01-01
A basic problem, which is of considerable interest in geoastrophysical applications of magnetogasdynamics, is the nonlinear interaction of a fast shock (S sub f) with a tangential discontinuity (T). The problem is treated for an arbitrary S sub f interacting with an arbitrary T under the assumption that in the frame of reference in which S sub f and T are at rest, the flow is superfast on both sides of T, and that a steady flow develops. As a result of the nonlinear analysis a flow pattern is obtained consisting of the incident discontinuities S sub f 1 and T2 and a transmitted fast shock S sub f 3, the modified tangential discontinuity T4 and a reflected fast shock S sub f 5 or fast rarefaction wave R sub f 5. The results are discussed in terms of seven significant similarity parameters. In addition special cases like changes in magnetic field direction only, changes in desnity or velocity shear only etc. are discussed.
In-situ observations of nonlinear wave particle interaction of electromagnetic ion cyclotron waves
NASA Astrophysics Data System (ADS)
Shoji, M.; Miyoshi, Y.; Keika, K.; Katoh, Y.; Angelopoulos, V.; Nakamura, S.; Omura, Y.
2014-12-01
Direct measurement method for the electromagnetic wave and space plasma interaction has been suggested by a computer simulation study [Katoh et al., 2013], so-called Wave Particle Interaction Analysis (WPIA). We perform the WPIA for rising tone electromagnetic ion cyclotron (EMIC) waves (so-called EMIC triggered emissions), of which generation mechanism is essentially the same as the chorus emissions. THEMIS observation data (EFI, FGM, and ESA) are used for the WPIA. In the WPIA, we calculate (1) the inner product of the wave electric field and the velocity of the energetic protons: Wint, (2) the inner product of the wave magnetic field and the velocity of the energetic protons: WBint, and (3) the phase angle ζ between the wave magnetic field and the perpendicular velocity of the energetic protons. The values of (1) and (2) indicate the existence of the resonant currents inducing the nonlinear wave growth and the frequency change, respectively. We find the negative Wint and positive WBint at the nonlinear growing phase of the triggered emission as predicted in the theory [e.g. Omura and Nunn, 2011, Shoji and Omura, 2013]. In histogram of (3), we show the existence of the electromagnetic proton holes in the phase space generating the resonant currents. We also perform a hybrid simulation and evaluate WPIA method for EMIC waves. The simulation results show good agreement with the in-situ THEMIS observations.
Huang, Hong-Zhong; Yuan, Rong
2014-01-01
Many structures are subjected to variable amplitude loading in engineering practice. The foundation of fatigue life prediction under variable amplitude loading is how to deal with the fatigue damage accumulation. A nonlinear fatigue damage accumulation model to consider the effects of load sequences was proposed in earlier literature, but the model cannot consider the load interaction effects, and sometimes it makes a major error. A modified nonlinear damage accumulation model is proposed in this paper to account for the load interaction effects. Experimental data of two metallic materials are used to validate the proposed model. The agreement between the model prediction and experimental data is observed, and the predictions by proposed model are more possibly in accordance with experimental data than that by primary model and Miner's rule. Comparison between the predicted cumulative damage by the proposed model and an existing model shows that the proposed model predictions can meet the accuracy requirement of the engineering project and it can be used to predict the fatigue life of welded aluminum alloy joint of Electric Multiple Units (EMU); meanwhile, the accuracy of approximation can be obtained from the proposed model though more simple computing process and less material parameters calling for extensive testing than the existing model. PMID:24574866
ERIC Educational Resources Information Center
Prosser, Andrew
2014-01-01
Digital storytelling is already used extensively in language education. Web documentaries, particularly in terms of design and narrative structure, provide an extension of the digital storytelling concept, specifically in terms of increased interactivity. Using a model of interactive, non-linear storytelling, originally derived from computer game…
Nonlinear interaction of proton whistler with kinetic Alfvén wave to study solar wind turbulence
Goyal, R.; Sharma, R. P.; Goldstein, M. L.; Dwivedi, N. K.
2013-12-15
This paper presents the nonlinear interaction between small but finite amplitude kinetic Alfvén wave (KAW) and proton whistler wave using two-fluid model in intermediate beta plasma, applicable to solar wind. The nonlinearity is introduced by modification in the background density. This change in density is attributed to the nonlinear ponderomotive force due to KAW. The solutions of the model equations, governing the nonlinear interaction (and its effect on the formation of localized structures), have been obtained using semi-analytical method in solar wind at 1AU. It is concluded that the KAW properties significantly affect the threshold field required for the filament formation and their critical size (for proton whistler). The magnetic and electric field power spectra have been obtained and their relevance with the recent observations of solar wind turbulence by Cluster spacecraft has been pointed out.
Wang Xiuli; Zhang Jinxia; Liu Guocheng; Lin Hongyan
2011-02-15
Seven new Cd(II) complexes consisting of different phenanthroline derivatives and organic acid ligands, formulated as [Cd(PIP){sub 2}(dnba){sub 2}] (1), [Cd(PIP)(ox)].H{sub 2}O (2), [Cd(PIP)(1,4-bdc)(H{sub 2}O)].4H{sub 2}O (3), [Cd(3-PIP){sub 2}(H{sub 2}O){sub 2}].4H{sub 2}O (4), [Cd{sub 2}(3-PIP){sub 4}(4,4'-bpdc)(H{sub 2}O){sub 2}].5H{sub 2}O (5), [Cd(3-PIP)(nip)(H{sub 2}O)].H{sub 2}O (6), [Cd{sub 2}(TIP){sub 4}(4,4'-bpdc)(H{sub 2}O){sub 2}].3H{sub 2}O (7) (PIP=2-phenylimidazo[4,5-f]1,10-phenanthroline, 3-PIP=2-(3-pyridyl)imidazo[4,5-f]1,10-phenanthroline, TIP=2-(2-thienyl)imidazo[4,5-f]1,10-phenanthroline, Hdnba=3,5-dinitrobenzoic acid, H{sub 2}ox=oxalic acid, 1,4-H{sub 2}bdc=benzene-1,4-dicarboxylic acid, 4,4'-H{sub 2}bpdc=biphenyl-4,4'-dicarboxylic acid, H{sub 2}nip=5-nitroisophthalic acid) have been synthesized under hydrothermal conditions. Complexes 1 and 4 possess mononuclear structures; complexes 5 and 7 are isostructural and have dinuclear structures; complexes 2 and 3 feature 1D chain structures; complex 6 contains 1D double chain, which are further extended to a 3D supramolecular structure by {pi}-{pi} stacking and hydrogen bonding interactions. The N-donor ligands with extended {pi}-system and organic acid ligands play a crucial role in the formation of the final supramolecular frameworks. Moreover, thermal properties and fluorescence of 1-7 are also investigated. -- Graphical abstract: Seven new supramolecular architectures have been successfully isolated under hydrothermal conditions by reactions of different phen derivatives and Cd(II) salts together with organic carboxylate anions auxiliary ligands. Display Omitted Research highlights: {yields} Complexes 1-7 are 0D or 1D polymeric structure, the {pi}-{pi} stacking and H-bonding interactions extend the complexes into 3D supramolecular network. To our knowledge, systematic study on {pi}-{pi} stacking and H-bonding interactions in cadmium(II) complexes are still limited. {yields} The structural
He, F; Sarrigiannis, P G; Billings, S A; Wei, H; Rowe, J; Romanowski, C; Hoggard, N; Hadjivassilliou, M; Rao, D G; Grünewald, R; Khan, A; Yianni, J
2016-06-01
There is increasing evidence to suggest that essential tremor has a central origin. Different structures appear to be part of the central tremorogenic network, including the motor cortex, the thalamus and the cerebellum. Some studies using electroencephalogram (EEG) and magnetoencephalography (MEG) show linear association in the tremor frequency between the motor cortex and the contralateral tremor electromyography (EMG). Additionally, high thalamomuscular coherence is found with the use of thalamic local field potential (LFP) recordings and tremulous EMG in patients undergoing surgery for deep brain stimulation (DBS). Despite a well-established reciprocal anatomical connection between the thalamus and cortex, the functional association between the two structures during "tremor-on" periods remains elusive. Thalamic (Vim) LFPs, ipsilateral scalp EEG from the sensorimotor cortex and contralateral tremor arm EMG recordings were obtained from two patients with essential tremor who had undergone successful surgery for DBS. Coherence analysis shows a strong linear association between thalamic LFPs and contralateral tremor EMG, but the relationship between the EEG and the thalamus is much less clear. These measurements were then analyzed by constructing a novel parametric nonlinear autoregressive with exogenous input (NARX) model. This new approach uncovered two distinct and not overlapping frequency "channels" of communication between Vim thalamus and the ipsilateral motor cortex, defining robustly "tremor-on" versus "tremor-off" states. The associated estimated nonlinear time lags also showed non-overlapping values between the two states, with longer corticothalamic lags (exceeding 50ms) in the tremor active state, suggesting involvement of an indirect multisynaptic loop. The results reveal the importance of the nonlinear interactions between cortical and subcortical areas in the central motor network of essential tremor. This work is important because it demonstrates
NASA Astrophysics Data System (ADS)
Hayata, K.; Koshiba, M.
1995-11-01
We show analytically that inclusion of contributions from third-order nonlinearities in a theoretical model for optical parametric interactions derived from second-order nonlinearities makes possible the prediction of various kinds of stationary solitary-wave solution. Specifically these waves consist of hyperbolic (bright and dark types), algebraic (bright and dark types), and kink/antikink types. In the limit of vanishing third-order nonlinearities the first solitary-wave family (hyperbolic type) is reduced to solitary waves already reported. Effects of dissipations including one- and two-photon absorption are discussed as well. Copyright (c) 1995 Optical Society of America
Accetta, Alessandro; Petrovic, Ana G; Marchelli, Rosangela; Berova, Nina; Corradini, Roberto
2015-12-01
Parallel PNA:PNA duplexes were synthesized and conjugated with meso-tris(pyridyl)phenylporphyrin carboxylic acid at the N-terminus. The introduction of one porphyrin unit was shown to affect slightly the stability of the PNA:PNA parallel duplex, whereas the presence of two porphyrin units at the same end resulted in a dramatic increase of the melting temperature, accompanied by hysteresis between melting and cooling curves. The circular dichroism (CD) profile of the Soret band and fluorescence quenching strongly support the occurrence of a face-to-face interaction between the two porphyrin units. Introduction of a L-lysine residue at the C-terminal of one strand of the parallel duplex induced a left-handed helical structure in the PNA:PNA duplex if the latter contains only one or no porphyrin moiety. The left-handed helicity was revealed by nucleobase CD profile at 240-280 nm and by the induced-CD observed in the presence of the DiSC2 (5) cyanine dye at ~500-550 nm. Surprisingly, the presence of two porphyrin units led to the disappearance of the nucleobase CD signal and the absence of CD exciton coupling within the Soret band region. In addition, a dramatic decrease of induced CD of DiSC2 (5) was observed. These results are in agreement with a model where the porphyrin-porphyrin interactions cause partial loss of chirality of the PNA:PNA parallel duplex, forcing it to adopt a ladder-like conformation. PMID:26412743
Large eddy simulations and experiments of nonlinear flow interactions in hybrid rocket combustion
NASA Astrophysics Data System (ADS)
Na, Y.; Lee, C.
2013-03-01
Nonlinear combustion phenomenon was investigated through an experiment in a hybrid rocket motor. A poly(methyl methacrylate) (PMMA) / gaseous oxygen (GOx) combination was used with several types of disks equipped in a prechamber with the aim of modifying the local turbulent flow. By allowing this disturbance generated in a prechamber to interact with the shedding vortex inherently produced in the main chamber, a possibility of commonly observed nonlinear combustion feature such as DC-shift was analyzed. In a baseline test, a vortex shedding occurs due to the interaction of a main oxidizer flow with the evaporated fuel stream coming out of the surface during the regression process. Among the several types of disks, it turned out that only the disk4 produced the excitation which subsequently suppressed the vortex shedding phenomenon in the main chamber. This descent interaction was reflected in a sudden pressure drop (which may be described as direct current (DC) shift) of about 10 psi in the time history of the pressure during the nominal combustion. The present result with the disk4 suggests the possibility of phase cancellation between the excitation induced by the disk4 and the shedding vortex but much more work should be conducted to extract more accurate correlation of the phase information. In order to understand the baseline flow physics, a compressible large eddy simulation (LES) was conducted with the prescribed wall blowing boundary condition. The result clearly exhibited the existence of vortex shedding phenomenon with a specified frequency. The fact that important flow features of the present computation are quite similar to those obtained with an incompressible assumption in a flat channel suggests that both compressibility and curvature effects do not dominate in the present flow configuration.
NASA Astrophysics Data System (ADS)
Massin, F.; Farrell, J.; Smith, R. B.; Shelly, D. R.
2012-12-01
Abnormally high earthquake rates and episodic crustal deformation suggest that the Yellowstone hotspot affects the tectonics of the western United States. However the relationship between the Yellowstone volcanic system and the surrounding tectonic regime remains poorly known. We study the structure and stress field for quantitative modeling of volcano-tectonic interactions using multiplet analysis. Our analysis shows that earthquake rates of Yellowstone are coincident with the uplift and subsidence episodes of the 0.64 Ma Yellowstone caldera: a relative decrease of multiplet activity accompanies each subsidence episode between 1997 and 2010. Our research focuses on the determination of crustal seismogenic structures and related stress perturbations that are responsible for the abnormally intense and cyclic earthquake activity. We consider each multiplet as a homogenous set of earthquakes produced by the same seismic source or fault. We integrate results from double-difference hypocenter relocations and source mechanism determinations to evaluate active fault properties. Hypocenters are constrained by a median of 50 P-wave and 12 S-wave differential arrival times (up to 4062 P-waves and 1187 S-waves). Composite focal mechanism solutions are determined for multiplets with 64 P-wave polarity observations or more. We compare multilinear regression planes of hypocenters of large multiplets and their composite focal mechanisms to choose fault planes and slip directions. We then develop detailed analysis of the largest earthquake swarms in Yellowstone, e.g. the Autumn 1985, the 2008 Yellowstone Lake and the 2010 Madison Plateau earthquake swarms to examine if swarm earthquakes occur on one continuous fault plane or on a network of independent segments with variable orientations. To independently confirm the interpreted fault plane we also invert for the moment tensors of the largest multiplets with a cumulative seismic moment over Mw3. The moment tensors are decomposed
Fluid-structure interaction for nonlinear response of shells conveying pulsatile flow
NASA Astrophysics Data System (ADS)
Tubaldi, Eleonora; Amabili, Marco; Païdoussis, Michael P.
2016-06-01
Circular cylindrical shells with flexible boundary conditions conveying pulsatile flow and subjected to pulsatile pressure are investigated. The equations of motion are obtained based on the nonlinear Novozhilov shell theory via Lagrangian approach. The flow is set in motion by a pulsatile pressure gradient. The fluid is modeled as a Newtonian pulsatile flow and it is formulated using a hybrid model that contains the unsteady effects obtained from the linear potential flow theory and the pulsatile viscous effects obtained from the unsteady time-averaged Navier-Stokes equations. A numerical bifurcation analysis employs a refined reduced order model to investigate the dynamic behavior. The case of shells containing quiescent fluid subjected to the action of a pulsatile transmural pressure is also addressed. Geometrically nonlinear vibration response to pulsatile flow and transmural pressure are here presented via frequency-response curves and time histories. The vibrations involving both a driven mode and a companion mode, which appear due to the axial symmetry, are also investigated. This theoretical framework represents a pioneering study that could be of great interest for biomedical applications. In particular, in the future, a more refined model of the one here presented will possibly be applied to reproduce the dynamic behavior of vascular prostheses used for repairing and replacing damaged and diseased thoracic aorta in cases of aneurysm, dissection or coarctation. For this purpose, a pulsatile time-dependent blood flow model is here considered by applying physiological waveforms of velocity and pressure during the heart beating period. This study provides, for the first time in literature, a fully coupled fluid-structure interaction model with deep insights in the nonlinear vibrations of circular cylindrical shells subjected to pulsatile pressure and pulsatile flow.
A Nonlinear Model for Gene-Based Gene-Environment Interaction.
Sa, Jian; Liu, Xu; He, Tao; Liu, Guifen; Cui, Yuehua
2016-01-01
A vast amount of literature has confirmed the role of gene-environment (G×E) interaction in the etiology of complex human diseases. Traditional methods are predominantly focused on the analysis of interaction between a single nucleotide polymorphism (SNP) and an environmental variable. Given that genes are the functional units, it is crucial to understand how gene effects (rather than single SNP effects) are influenced by an environmental variable to affect disease risk. Motivated by the increasing awareness of the power of gene-based association analysis over single variant based approach, in this work, we proposed a sparse principle component regression (sPCR) model to understand the gene-based G×E interaction effect on complex disease. We first extracted the sparse principal components for SNPs in a gene, then the effect of each principal component was modeled by a varying-coefficient (VC) model. The model can jointly model variants in a gene in which their effects are nonlinearly influenced by an environmental variable. In addition, the varying-coefficient sPCR (VC-sPCR) model has nice interpretation property since the sparsity on the principal component loadings can tell the relative importance of the corresponding SNPs in each component. We applied our method to a human birth weight dataset in Thai population. We analyzed 12,005 genes across 22 chromosomes and found one significant interaction effect using the Bonferroni correction method and one suggestive interaction. The model performance was further evaluated through simulation studies. Our model provides a system approach to evaluate gene-based G×E interaction. PMID:27271617
A Nonlinear Model for Gene-Based Gene-Environment Interaction
Sa, Jian; Liu, Xu; He, Tao; Liu, Guifen; Cui, Yuehua
2016-01-01
A vast amount of literature has confirmed the role of gene-environment (G×E) interaction in the etiology of complex human diseases. Traditional methods are predominantly focused on the analysis of interaction between a single nucleotide polymorphism (SNP) and an environmental variable. Given that genes are the functional units, it is crucial to understand how gene effects (rather than single SNP effects) are influenced by an environmental variable to affect disease risk. Motivated by the increasing awareness of the power of gene-based association analysis over single variant based approach, in this work, we proposed a sparse principle component regression (sPCR) model to understand the gene-based G×E interaction effect on complex disease. We first extracted the sparse principal components for SNPs in a gene, then the effect of each principal component was modeled by a varying-coefficient (VC) model. The model can jointly model variants in a gene in which their effects are nonlinearly influenced by an environmental variable. In addition, the varying-coefficient sPCR (VC-sPCR) model has nice interpretation property since the sparsity on the principal component loadings can tell the relative importance of the corresponding SNPs in each component. We applied our method to a human birth weight dataset in Thai population. We analyzed 12,005 genes across 22 chromosomes and found one significant interaction effect using the Bonferroni correction method and one suggestive interaction. The model performance was further evaluated through simulation studies. Our model provides a system approach to evaluate gene-based G×E interaction. PMID:27271617
Towards modeling of nonlinear laser-plasma interactions with hydrocodes: the thick-ray approach.
Colaïtis, A; Duchateau, G; Nicolaï, P; Tikhonchuk, V
2014-03-01
This paper deals with the computation of laser beam intensity in large-scale radiative hydrocodes applied to the modeling of nonlinear laser-plasma interactions (LPIs) in inertial confinement fusion (ICF). The paraxial complex geometrical optics (PCGO) is adapted for light waves in an inhomogeneous medium and modified to include the inverse bremsstrahlung absorption and the ponderomotive force. This thick-ray model is compared to the standard ray-tracing (RT) approach, both in the chic code. The PCGO model leads to different power deposition patterns and better diffraction modeling compared to standard RT codes. The intensity-reconstruction technique used in RT codes to model nonlinear LPI leads to artificial filamentation and fails to reproduce realistic ponderomotive self-focusing distances, intensity amplifications, and density channel depletions, whereas PCGO succeeds. Bundles of Gaussian thick rays can be used to model realistic non-Gaussian ICF beams. The PCGO approach is expected to improve the accuracy of ICF simulations and serve as a basis to implement diverse LPI effects in large-scale hydrocodes. PMID:24730950
Nonlinear electron magnetohydrodynamics physics. II. Wave propagation and wave-wave interactions
Urrutia, J. M.; Stenzel, R. L.; Strohmaier, K. D.
2008-04-15
The propagation of low-frequency whistler modes with wave magnetic field exceeding the ambient field is investigated experimentally. Such nonlinear waves are excited with magnetic loop antennas whose axial field is aligned with the background magnetic field and greatly exceeds its strength. The oscillatory antenna field excites propagating wave packets with field topologies alternating between whistler spheromaks and mirrors. The propagation speed of spheromaks is observed to decrease with amplitude while that of mirrors increases with amplitude. The field distribution varies with amplitude: Spheromaks contract axially while mirrors spread out compared to linear whistlers. Consequently, the peak magnetic field and current densities in spheromaks exceed that of mirrors. Wave-wave interactions of nonlinear whistler modes is also studied. Counterpropagating spheromaks collide inelastically and form a stationary field-reversed configuration. The radius of the toroidal current ring depends on current and can be larger than that of the loop antenna. A tilted field-reversed configuration precesses in the direction of the electron drift. The free magnetic energy is dissipated in the plasma volume and converted into electron heat.
Numerical simulation of nonlinear mode interactions in ridge-waveguide semiconductor lasers
NASA Astrophysics Data System (ADS)
Kalagara, Hemashilpa; Eliseev, Petr G.; Osinski, Marek
2012-02-01
Nonlinear perturbation of effective group index is calculated numerically in semiconductor ridge waveguide laser structures under an influence of a strong driving wave (mode). Model of nonlinear interaction of waves is used to obtain conditions for appearance of anomalous dispersion of modal index and also for inversion of the group index of guided waves (modes of the ridge-waveguide laser structures). Ranges around critically anomalous dispersion (CAD) points, where the effective group index passes zero value, are calculated numerically. CAD points form closed loops in graphs of detuning vs. driving wave intensity. These loops define ranges where superluminal propagation, as well as slowed reflection of probe wave can be obtained. Numerical simulations are performed for an InGaAs/AlGaAs/GaAs double quantum well (DQW) laser structure and also for a GaAs/AlGaAs separate confinement heterostructure. The threshold intensities for the appearance of CAD points, as well as the influence of relaxation rate and optical confinement on the appearance of superluminal regime are compared for the DQW and SCH structures.
NASA Astrophysics Data System (ADS)
Zhong, Rong-Lin; Xu, Hong-Liang; Li, Zhi-Ru
2016-08-01
An increasing number of chemists have focused on the two-electron/multicenter bond (2e/mc) that was first introduced to interpret the bonding mechanism of radical dimers. Herein, we report the polar two-electron/twelve center (2e/12c) bonding character in a series of phenalenyl-azaphenalenyl radical hetero-dimers. Interestingly, the bonding energy of weaker polar hetero-dimer (P-TAP) is dominated by the overlap of the two different singly occupied molecular orbital of radicals, while that of stronger polar hetero-dimer (P-HAP) is dominated by the electrostatic attraction. Results show that the difference between the electronegativity of the monomers plays a prominent role in the essential attribution of the polar 2e/12c bond. Correspondingly, a stronger stacking interaction in the hetero-dimer could be effectively achieved by increasing the difference of nitrogen atoms number between the monomers. It is worthy of note that an interesting interlayer charge transfer character is induced in the polar hetero-dimers, which is dependent on the difference between the electronegativity of the monomers. It is our expectation that the new knowledge about the bonding nature of radical hetero-dimers might provide important information for designing radical based functional materials with various applications.
Non-linear dynamic interactions of a Jeffcott rotor with preloaded snubber ring
NASA Astrophysics Data System (ADS)
Pavlovskaia, E. E.; Karpenko, E. V.; Wiercigroch, M.
2004-09-01
A two-degrees-of-freedom model of a Jeffcott rotor with a preloaded snubber ring subjected to out-of-balance excitation has been developed. The purely impact interactions have been investigated. The rotor makes intermittent contacts with the preloaded snubber ring and as a consequence it can be in one of five different contact regimes, which boundaries have been found analytically. The current location of the snubber ring has been determined using the principle of the minimum elastic energy in the snubber ring. Consequently a non-linear piecewise smooth dynamical system has been obtained and studied numerically. The results in form of bifurcation diagrams, phase portraits and Poincaré maps show significant differences for the cases with and without preloading.
Non-linear interactions of plasma waves in the context of solar particle acceleration
NASA Astrophysics Data System (ADS)
Gallegos-Cruz, A.; Perez-Peraza, J.
2001-08-01
Stochastic particle acceleration in plasmas by means of MHD turbulence in-volves a wide range of alternatives according to, the specific wave mode, the frequency regime of the turbulence, the kind of particles to be accelerated, the assumed plasma model and so on. At present most of the alternatives have been studied with relatively deepness, though some features are not yet com-pletely understood. One of them is the delimitation of the real importance of non-lineal effects of turbulence waves in the process of particle acceleration. In this work we analyse such effects taking into account the temporal evolution of the turbulence. For illustration we exemplify our analysis with the fast MHD mode. Our results show that in some specific stages of the turbulence evolu-tion, non-linear interactions have important effects in the process of particle acceleration.
Evidence for nonlinear wave-wave interactions in solar type III radio bursts
NASA Technical Reports Server (NTRS)
Lin, R. P.; Levedahl, W. K.; Lotko, W.; Gurnett, D. A.; Scarf, F. L.
1986-01-01
Evidence is presented that nonlinear wave-wave interactions occur in type III solar radio bursts. Intense, spiky Langmuir waves are observed to be driven by electron beams associated with type III solar radio bursts in the interplanetary medium. Bursts of 30-300 Hz (in the spacecraft frame) waves are often observed coincident in time with the most intense spikes of the Langmuir waves. These low-frequency waves appear to be long-wavelength ion acoustic waves, with wavenumber approximately equal to the beam resonant Langmuir wavenumber. Three possible interpretations of these observations are considered: modulational instability, parametric decay of the parent Langmuir waves to daughter ion acoustic and Langmuir waves, and decay to daughter electromagnetic waves and ion acoustic waves.
Nuclear quadrupole interaction and nonlinear optical property of some borate crystals^*
NASA Astrophysics Data System (ADS)
Choh, S. H.; Kim, I. G.; Shin, H. W.; Park, I.-W.
2003-03-01
Borate crystals, like Li_2B_4O_7, LiB_3O_5, and BaB_2O_4, consist of 4-coordinated and/or 3-coordinated boron-oxygen bonds. As reported [1], the principal Z-axis of the electric field gradient (EFG) around the boron in 3-coordinated bonds is perpendicular to the plane containing the boron-oxygen bonds. We calculated the principal Z-direction of the EFG-tensor by employing the simple point charge model for the arbitrary planar triangle configurations, and the results are consistent with experimental ones. Moreover, a strong correlation between the nonlinear optical coefficient and the nuclear quadrupole interactions, such as the quadrupole coupling constant and the asymmetry parameter, was empirically found for these compounds. Details will be presented. * Supported by the National Research Laboratory Program(MOST). [1] I. G. Kim and S. H. Choh, J. Phys.: Condens. Matter, b11, 8283 (1999).
Nonlinear interaction of energetic ring current protons with magnetospheric hydromagnetic waves
Chan, A.A.; Chen, Liu; White, R.B.
1989-09-01
In order to study nonlinear wave-particle interactions in the earth's magnetosphere we have derived Hamiltonian equations for the gyrophase-averaged nonrealistic motion of charged particles in a perturbed dipole magnetic field. We assume low frequency (less than the proton gyrofrequency) fully electromagnetic perturbations, and we retain finite Larmor radius effects. Analytic and numerical results for the stochastic threshold of energetic protons ({approx gt} 100 keV) in compressional geomagnetic pulsations in the Pc 5 range of frequencies (150--600 seconds) are presented. These protons undergo a drift-bounce resonance with the Pc 5 waves which breaks the second (longitudinal) and third (flux) adiabatic invariants, while the first invariant (the magnetic moment) and the proton energy are approximately conserved. The proton motion in the observed spectrum of waves is found to be strongly diffusive, due to the overlap of neighboring primary resonances. 17 refs., 2 figs.
Nonlinear interaction of energetic ring current protons with magnetospheric hydromagnetic waves
Chan, A.A.; Chen, L.; White, R.B. )
1989-10-01
In order to study nonlinear wave-particle interactions in the Earth's magnetosphere we have derived Hamiltonian equations for the gyrophase-averaged nonrelativistic motion of charged particles in a perturbed dipole magnetic field. We assume low frequency (less than the proton gyrofrequency) fully electromagnetic perturbations, and we retain finite Larmor radius effects. Analytic and numerical results for the stochastic threshold of energetic protons ({approx gt}100 keV) in compressional geomagnetic pulsations in the Pc 5 range of frequencies 150--600 seconds are presented. These protons undergo a drift-bounce resonance with the Pc 5 waves which breaks the second (longitudinal) and third (flux) adiabatic invariants, while the first invariant (the magnetic moment) and the proton energy are approximately conserved. The proton motion in the observed spectrum of waves is found to be strongly diffusive, due to the overlap of neighboring primary resonances. {copyright} American Geophysical Union 1989
A simple method for wind tunnel balance calibration including non-linear interaction terms
NASA Astrophysics Data System (ADS)
Ramaswamy, M. A.; Srinivas, T.; Holla, V. S.
The conventional method for calibrating wind tunnel balances to obtain the coupled linear and nonlinear interaction terms requires the application of combinations of pure components of the loads on the calibration body compensating the deflection of the balance. For a six-component balance, this calls for a complex loading system and an arrangement to translate and tilt the balance support about all three axes. A simple method called the least-square method is illustrated for a three-component balance. The simplicity arises from the fact that application of the pure components of the loads or reorientation of the balance is not required. A single load is applied that has various components whose magnitudes can be easily found knowing the orientation of the calibration body under load and the point of application of the load. The coefficients are obtained by using the least-square-fit approach to match the outputs obtained for various combinations of load.
Linear and nonlinear interactions between the earth tide and a tectonically stressed earth
NASA Technical Reports Server (NTRS)
Beaumont, C.
1978-01-01
In the vincinity of earthquake focal regions, conditions may not be equal. Crustal rocks stressed to more than approximately 0.6 of their failure strength exhibit material properties over and above that of linear elasticity. Interactions between the earth tide and crustal rocks that are under high tectonic stress are discussed in terms of simple phenomenological models. In particular, the difference between a nonlinear elastic model of dilatancy and a dilatancy model that exhibits hysteresis is noted. It is concluded that the small changes in stress produced by the earth tide act as a probe of the properties of crustal rocks. Observations of earth tide tilts and strains in such high stress zones may, therefore, provide keys to the constitutive properties and the tectonic stress rate tensor of these zones.
Unraveling Base Stacking Driving Forces in DNA.
Mak, Chi H
2016-07-01
Base stacking is a key determinant of nucleic acid structures, but the precise origin of the thermodynamic driving force behind the stacking of nucleobases remains open. The rather mild stacking free energy measured experimentally, roughly a kcal/mol depending on the identity of the bases, is physiologically significant because while base stacking confers stability to the genome in its double helix form, the duplex also has to be unwound in order to be replicated or transcribed. A stacking free energy that is either too high or too low will over- or understabilize the genome, impacting the storage of genetic information and also its retrieval. While the molecular origin of stacking driving force has been attributed to many different sources including dispersion, electrostatics, and solvent hydrogen bonding, here we show via a systematic decomposition of the stacking free energy using large-scale computer simulations that the dominant driving force stabilizing base stacking is nonhydrophobic solvent entropy. Counteracting this is the conformational entropic penalty on the sugar-phosphate backbone against stacking, while solvent hydrogen-bonding, charge-charge interactions, and dispersive forces produce only secondary perturbations. Solvent entropic forces and DNA backbone conformational strains therefore work against each other, leading to a very mild composite stacking free energy in agreement with experiments. PMID:27045853
NASA Astrophysics Data System (ADS)
Rury, Aaron S.
2016-06-01
This study reports experimental, computational, and theoretical evidence for a previously unobserved coherent phonon-phonon interaction in an organic solid that can be described by the application of Fano's analysis to a case without the presence of a continuum. Using Raman spectroscopy of the hydrogen-bonded charge-transfer material quinhydrone, two peaks appear near 700 cm-1 we assign as phonons whose position and line-shape asymmetry depend on the sample temperature and light scattering excitation energy. Density functional theory calculations find two nearly degenerate phonons possessing frequencies near the values found in experiment that share similar atomic motion out of the aromatic plane of electron donor and acceptor molecules of quinhydrone. Further analytical modeling of the steady-state light scattering process using the Peierls-Hubbard Hamiltonian and time-dependent perturbation theory motivates assignment of the physical origin of the asymmetric features of each peak's line shape to an interaction between two discrete phonons via nonlinear electron-phonon coupling. In the context of analytical model results, characteristics of the experimental spectra upon 2.33 eV excitation of the Raman scattering process are used to qualify the temperature dependence of the magnitude of this coupling in the valence band of quinhydrone. These results broaden the range of phonon-phonon interactions in materials in general while also highlighting the rich physics and fundamental attributes specific to organic solids that may determine their applicability in next generation electronics and photonics technologies.
Ion-π interaction in impacting the nonlinear optical properties of ion-buckybowl complexes.
Chen, He; Wang, Wen-Yong; Wang, Li; Zhu, Chang-Li; Fang, Xin-Yan; Qiu, Yong-Qing
2016-03-01
Ion-buckybowl complexes have received considerable attention in modern chemical research due to its fundamental and practical importance. Herein, we performed density functional theory (DFT) to calculate the geometical structure, binding interactions, dipole moments and the first hyperpolarizabilities (βtot) of ion-buckybowl complexes (ions are Cl(-) and Na(+), buckybowls are quadrannulene, corannulene and sumanene). It is found that the stabilities of ion-buckybowl compounds primarily originate from the interaction energy, which was proved by a new isomerization energy decomposition analysis approach. Plots of reduced density gradient mirror the ion-π weak interaction has been formed between the ions and buckybowls. Significantly, the buckybowl subunits cannot effectively impact the nonlinear optical (NLO), but the kind of ion has marked influence on the second-order NLO responses. The βtot values of Cl(-)-buckybowl complexes are all larger as compared to that of Na(+)-buckybowl complexes, which is attributed to the large charge-transfer (CT) from Cl(-) to buckybowl. Our present work will be beneficial for further theoretical and experimental studies on the NLO properties of ion-buckybowl compounds. PMID:26851864
Adaptive nonlinear polynomial neural networks for control of boundary layer/structural interaction
NASA Technical Reports Server (NTRS)
Parker, B. Eugene, Jr.; Cellucci, Richard L.; Abbott, Dean W.; Barron, Roger L.; Jordan, Paul R., III; Poor, H. Vincent
1993-01-01
The acoustic pressures developed in a boundary layer can interact with an aircraft panel to induce significant vibration in the panel. Such vibration is undesirable due to the aerodynamic drag and structure-borne cabin noises that result. The overall objective of this work is to develop effective and practical feedback control strategies for actively reducing this flow-induced structural vibration. This report describes the results of initial evaluations using polynomial, neural network-based, feedback control to reduce flow induced vibration in aircraft panels due to turbulent boundary layer/structural interaction. Computer simulations are used to develop and analyze feedback control strategies to reduce vibration in a beam as a first step. The key differences between this work and that going on elsewhere are as follows: that turbulent and transitional boundary layers represent broadband excitation and thus present a more complex stochastic control scenario than that of narrow band (e.g., laminar boundary layer) excitation; and secondly, that the proposed controller structures are adaptive nonlinear infinite impulse response (IIR) polynomial neural network, as opposed to the traditional adaptive linear finite impulse response (FIR) filters used in most studies to date. The controllers implemented in this study achieved vibration attenuation of 27 to 60 dB depending on the type of boundary layer established by laminar, turbulent, and intermittent laminar-to-turbulent transitional flows. Application of multi-input, multi-output, adaptive, nonlinear feedback control of vibration in aircraft panels based on polynomial neural networks appears to be feasible today. Plans are outlined for Phase 2 of this study, which will include extending the theoretical investigation conducted in Phase 2 and verifying the results in a series of laboratory experiments involving both bum and plate models.
NASA Astrophysics Data System (ADS)
Sodha, Mahendra Singh; Mishra, Rashmi; Srivastava, Sweta
2016-03-01
In this paper, we consider the nonlinearity in the propagation of electromagnetic (e.m.) waves in a plasma caused by the electron temperature dependence of the coefficient of recombination of electrons with ions; specifically, the ionospheric E layer has been investigated. The enhancement in electron temperature by an intense electromagnetic wave causes reduction of the electron-ion recombination coefficient and thereby enhancement of electron density, the electron collision frequency also gets enhanced. The equations for number and energy balance of electrons and the wave equation have been used to predict the dependence of electron density/collision frequency and the nonlinear refractive index and absorption coefficient on αE02 (proportional to wave irradiance). The dependence of the propagation parameters on αE02 has been used to investigate the nonlinear electromagnetic wave propagation in the ionosphere. The study concludes that the electron temperature dependence of the recombination coefficient should be considered in all analyses of nonlinear plasma-e.m. wave interaction.
Xiao, Li; Wang, Changhao; Ye, Xiang; Luo, Ray
2016-08-25
Continuum solvation modeling based upon the Poisson-Boltzmann equation (PBE) is widely used in structural and functional analysis of biomolecules. In this work, we propose a charge-central interpretation of the full nonlinear PBE electrostatic interactions. The validity of the charge-central view or simply charge view, as formulated as a vacuum Poisson equation with effective charges, was first demonstrated by reproducing both electrostatic potentials and energies from the original solvated full nonlinear PBE. There are at least two benefits when the charge-central framework is applied. First the convergence analyses show that the use of polarization charges allows a much faster converging numerical procedure for electrostatic energy and forces calculation for the full nonlinear PBE. Second, the formulation of the solvated electrostatic interactions as effective charges in vacuum allows scalable algorithms to be deployed for large biomolecular systems. Here, we exploited the charge-view interpretation and developed a particle-particle particle-mesh (P3M) strategy for the full nonlinear PBE systems. We also studied the accuracy and convergence of solvation forces with the charge-view and the P3M methods. It is interesting to note that the convergence of both the charge-view and the P3M methods is more rapid than the original full nonlinear PBE method. Given the developments and validations documented here, we are working to adapt the P3M treatment of the full nonlinear PBE model to molecular dynamics simulations. PMID:27146097
Nonlinear laser-matter interaction processes in long-scale-length plasmas
NASA Astrophysics Data System (ADS)
Seka, W.; Bahr, R. E.; Short, R. W.; Simon, A.; Craxton, R. S.; Montgomery, D. S.; Rubenchik, A. E.
1992-07-01
This paper reports on nonlinear laser-plasma interaction experiments using long-scale-length plasmas produced by the 24-beam OMEGA laser system operating at 351 nm. The experiments were carried out with distributed phase plates (DPP's) in all beams and with and without smoothing by spectral dispersion (SSD). Most of the beams were used to create a large preformed plasma, which had gradient scale lengths of ≤800 μm at electron densities below a quarter of the critical density nc and temperatures in excess of 1 keV. One of the beams, the ``interaction beam,'' was timed independently and tightly focused to intensities ˜1015 W/cm2. All beams had pulse durations of ˜0.6 nsec. The interaction processes studied were mainly Raman scattering and the two-plasmon decay (TPD) instability as evidenced by its characteristic 3/2-harmonic emission. Details of the Raman and 3/2-harmonic spectra are presented. Evidence was found for the TPD instability close to its Landau cutoff density at ˜ 0.2nc. Raman emission was narrow-band and observed only from densities < 0.2nc. For late timings of the interaction beam, the Raman emission appeared to originate from near the peak of the density profile, but for earlier timings it appeared to come from densities a factor of 2 below the calculated peak. Application of SSD affected the 3/2-harmonic emission only slightly, but it strongly reduced the Raman emission. A discussion is given of some models that attempt to explain these observations.
NASA Astrophysics Data System (ADS)
Nguyen, Vu A.; Palo, Scott E.; Lieberman, Ruth S.; Forbes, Jeffrey M.; Ortland, David A.; Siskind, David E.
2016-07-01
Theory and past observations have provided evidence that atmospheric tides and other global-scale waves interact nonlinearly to produce additional secondary waves throughout the space-atmosphere interaction region. However, few studies have investigated the generation region of nonlinearly generated secondary waves, and as a result, the manifestation and impacts of these waves are still poorly understood. This study focuses on the nonlinear interaction between the quasi 2 day wave (2dayW3) and the migrating diurnal tide (DW1), two of the largest global-scale waves in the atmosphere. The fundamental goals of this effort are to characterize the forcing region of the secondary waves and to understand how it relates to their manifestation on a global scale. First, the Fast Fourier Synoptic Mapping method is applied to Thermosphere Ionosphere Mesosphere Energetics and Dynamics-Sounding of the Atmosphere using Broadband Emission Radiometry satellite observations to provide new evidence of secondary waves. These results show that secondary waves are only significant above 80 km. The nonlinear forcing for each secondary wave is then computed by extracting short-term primary wave information from a reanalysis model. The estimated nonlinear forcing quantities are used to force a linearized tidal model in order to calculate numerical secondary wave responses. Model results show that the secondary waves are significant from the upper mesosphere to the middle thermosphere, highlighting the implications for the atmosphere-space weather coupling. The study also concludes that the secondary wave response is most sensitive to the nonlinear forcing occurring in the lower and middle mesosphere and not coincident with the regions of strongest nonlinear forcing.
Umeda, Takayuki
2008-06-15
Nonlinear evolution of the electron two-stream instability in a current-carrying plasma is examined by using a two-dimensional electromagnetic particle-in-cell simulation. Formation of electron phase-space holes is observed as an early nonlinear consequence of electron-beam-plasma interactions. Lower-hybrid waves, electrostatic, and electromagnetic whistler mode waves are also excited by different mechanisms during the ensuing nonlinear wave-particle interactions. It is shown by the present computer simulation with a large simulation domain and a long simulation time that these low-frequency waves can disturb the electrostatic equilibrium of electron phase-space holes, suggesting that the lifetime of electron phase-space holes sometimes becomes shorter in a current-carrying plasma.
The Role of Nonlinear Interactions in Causing Transitions into Edge Transport-Barrier Regimes
NASA Astrophysics Data System (ADS)
Cziegler, Istvan
2015-11-01
Transitions of tokamak confinement regimes are studied with a focus on interactions between turbulence and zonal flows (ZF) or geodesic-acoustic modes (GAM). Results show that access to im-proved confinement regimes is profoundly affected by these interactions and clarify the role of GAM and ZF in different types of transitions. In order to understand the underlying dynamics of these transitions, both their trigger mechanism and the parametric dependence of nonlinear transfer processes are studied using gas-puff-imaging. For the L-to-H transition, this work shows that the stress mediated transfer rate of kinetic energy from turbulence into ZF leads in the changes, the turbulence collapses, and finally the pressure gradient forms - establishing the trigger as flow organization. For the I-mode, turbulence is studied with the aim of understanding /emphaccess to the improved confinement regime, which exhibits an edge temperature pedestal, but a relaxed density profile. L-to-I and I-to-H transitions are analyzed in a time-resolved manner analogous to the L-H transition. For the L-to-I transition there is a difference between the scaling of the regime's typical edge fluctuation, the Weakly Coherent Mode (WCM), and GAM, known to be essential in shaping the WCM. Both the WCM and the GAM are necessary for the regime, and regime access is found to be sensitive to the GAM drive and damping. Parametric dependences of nonlinearities are examined in steady state discharges from a range of toroidal field, plasma current, and density; and interactions between flows and turbulence in both L-mode and I-mode are estimated using bispectral methods. The ZF drive increases monotonically with cross-field heat flux, i.e. approaches a transition, while GAM follow more complicated trends. These results advance our progress toward predicting the parametric dependences of transition conditions. Work supported by USDoE, Office of Science, Award Numbers DE-SC-0008689 and DE-FC02-99ER54512.
Neurosurgery simulation using non-linear finite element modeling and haptic interaction
NASA Astrophysics Data System (ADS)
Lee, Huai-Ping; Audette, Michel; Joldes, Grand R.; Enquobahrie, Andinet
2012-02-01
Real-time surgical simulation is becoming an important component of surgical training. To meet the realtime requirement, however, the accuracy of the biomechancial modeling of soft tissue is often compromised due to computing resource constraints. Furthermore, haptic integration presents an additional challenge with its requirement for a high update rate. As a result, most real-time surgical simulation systems employ a linear elasticity model, simplified numerical methods such as the boundary element method or spring-particle systems, and coarse volumetric meshes. However, these systems are not clinically realistic. We present here an ongoing work aimed at developing an efficient and physically realistic neurosurgery simulator using a non-linear finite element method (FEM) with haptic interaction. Real-time finite element analysis is achieved by utilizing the total Lagrangian explicit dynamic (TLED) formulation and GPU acceleration of per-node and per-element operations. We employ a virtual coupling method for separating deformable body simulation and collision detection from haptic rendering, which needs to be updated at a much higher rate than the visual simulation. The system provides accurate biomechancial modeling of soft tissue while retaining a real-time performance with haptic interaction. However, our experiments showed that the stability of the simulator depends heavily on the material property of the tissue and the speed of colliding objects. Hence, additional efforts including dynamic relaxation are required to improve the stability of the system.
NASA Astrophysics Data System (ADS)
Chiroux, Robert Charles
The objective of this research was to produce a three dimensional, non-linear, dynamic simulation of the interaction between a hyperelastic wheel rolling over compactable soil. The finite element models developed to produce the simulation utilized the ABAQUS/Explicit computer code. Within the simulation two separate bodies were modeled, the hyperelastic wheel and a compactable soil-bed. Interaction between the bodies was achieved by allowing them to come in contact but not to penetrate the contact surface. The simulation included dynamic loading of a hyperelastic, rubber tire in contact with compactable soil with an applied constant angular velocity or torque, including a tow load, applied to the wheel hub. The constraints on the wheel model produced a straight and curved path. In addition the simulation included a shear limit between the tire and soil allowing for the introduction of slip. Soil properties were simulated using the Drucker-Prager, Cap Plasticity model available within the ABAQUS/Explicit program. Numerical results obtained from the three dimensional model were compared with related experimental data and showed good correlation for similar conditions. Numerical and experimental data compared well for both stress and wheel rut formation depth under a weight of 5.8 kN and a constant angular velocity applied to the wheel hub. The simulation results provided a demonstration of the benefit of three-dimensional simulation in comparison to previous two-dimensional, plane strain simulations.
Optimal bipedal interactions with dynamic terrain: synthesis and analysis via nonlinear programming
NASA Astrophysics Data System (ADS)
Hubicki, Christian; Goldman, Daniel; Ames, Aaron
In terrestrial locomotion, gait dynamics and motor control behaviors are tuned to interact efficiently and stably with the dynamics of the terrain (i.e. terradynamics). This controlled interaction must be particularly thoughtful in bipeds, as their reduced contact points render them highly susceptible to falls. While bipedalism under rigid terrain assumptions is well-studied, insights for two-legged locomotion on soft terrain, such as sand and dirt, are comparatively sparse. We seek an understanding of how biological bipeds stably and economically negotiate granular media, with an eye toward imbuing those abilities in bipedal robots. We present a trajectory optimization method for controlled systems subject to granular intrusion. By formulating a large-scale nonlinear program (NLP) with reduced-order resistive force theory (RFT) models and jamming cone dynamics, the optimized motions are informed and shaped by the dynamics of the terrain. Using a variant of direct collocation methods, we can express all optimization objectives and constraints in closed-form, resulting in rapid solving by standard NLP solvers, such as IPOPT. We employ this tool to analyze emergent features of bipedal locomotion in granular media, with an eye toward robotic implementation.
Sadikov, G. G. Antsyshkina, A. S.; Rodnikova, M. N.; Solonina, I. A.
2009-01-15
Crystals of the compounds Yb(NO{sub 3}){sub 3}(Phen){sub 2} and La(NO{sub 3}){sub 3}(Phen){sub 2} (Phen = 1,10-phenanthroline) are investigated using X-ray diffraction. It is established that there exist two different crystalline modifications: the main modification (phase 1) is characteristic of all members of the isostructural series, and the second modification (phase 2) is observed only for the Eu, Er, and Yb elements. It is assumed that the stability and universality of main phase 1 are associated with the occurrence of the nonbonded {pi}-{pi} stacking interactions between the adjacent phenanthroline ligands in the complexes. The indication of the interactions is a distortion of the planar shape of the Phen molecule (the folding of the metallocycle along the N-N line with a folding angle of 11{sup o}-13{sup o} and its 'boomerang' distortion). The assumption regarding the {pi}-{pi} stacking interaction is very consistent with the shape of the ellipsoids of atomic thermal vibrations, as well as with the data obtained from thermography and IR spectroscopy. An analysis of the structures of a number of rare-earth compounds has demonstrated that the intracomplex {pi}-{pi} stacking interactions directly contribute to the formation of supramolecular associates in the crystals, such as molecular dimers, supramolecules, chain and layered ensembles, and framework systems.
NASA Astrophysics Data System (ADS)
Rashed, Mohamed
2014-06-01
Common-Mid-Point (CMP) stacking is a major process to enhance signal-to-noise ratio in seismic data. Since its appearance fifty years ago, CMP stacking has gone through different phases of prosperity and negligence within the geophysical community. During those times, CMP stacking developed from a simple process of averaging into a sophisticated process that involves complicated mathematics and state-of-the-art computation. This article summarizes the basic principles, assumptions, and violations related to the CMP stacking technique, presents a historical overview on the development stages of CMP stacking, and discusses its future potentiality.
Carter, T A
2006-11-16
Final report for DOE Plasma Physics Junior Faculty Development award DOE-FG02-02ER54688. Reports on research undertaken from 8/1/2002 until 5/15/2006, investigating nonlinear interactions between Alfven waves in a laboratory experiment.
ERIC Educational Resources Information Center
Strang, Kenneth David
2009-01-01
This paper discusses how a seldom-used statistical procedure, recursive regression (RR), can numerically and graphically illustrate data-driven nonlinear relationships and interaction of variables. This routine falls into the family of exploratory techniques, yet a few interesting features make it a valuable compliment to factor analysis and…
NASA Astrophysics Data System (ADS)
Wang, Xiuli; Zhang, Jinxia; Liu, Guocheng; Lin, Hongyan
2011-02-01
Seven new Cd(II) complexes consisting of different phenanthroline derivatives and organic acid ligands, formulated as [Cd(PIP) 2(dnba) 2] ( 1), [Cd(PIP)(ox)]·H 2O ( 2), [Cd(PIP)(1,4-bdc)(H 2O)]·4H 2O ( 3), [Cd(3-PIP) 2(H 2O) 2]·4H 2O ( 4), [Cd 2(3-PIP) 4(4,4'-bpdc)(H 2O) 2]·5H 2O ( 5), [Cd(3-PIP)(nip)(H 2O)]·H 2O ( 6), [Cd 2(TIP) 4(4,4'-bpdc)(H 2O) 2]·3H 2O ( 7) (PIP=2-phenylimidazo[4,5- f]1,10-phenanthroline, 3-PIP=2-(3-pyridyl)imidazo[4,5- f]1,10-phenanthroline, TIP=2-(2-thienyl)imidazo[4,5- f]1,10-phenanthroline, Hdnba=3,5-dinitrobenzoic acid, H 2ox=oxalic acid, 1,4-H 2bdc=benzene-1,4-dicarboxylic acid, 4,4'-H 2bpdc=biphenyl-4,4'-dicarboxylic acid, H 2nip=5-nitroisophthalic acid) have been synthesized under hydrothermal conditions. Complexes 1 and 4 possess mononuclear structures; complexes 5 and 7 are isostructural and have dinuclear structures; complexes 2 and 3 feature 1D chain structures; complex 6 contains 1D double chain, which are further extended to a 3D supramolecular structure by π- π stacking and hydrogen bonding interactions. The N-donor ligands with extended π-system and organic acid ligands play a crucial role in the formation of the final supramolecular frameworks. Moreover, thermal properties and fluorescence of 1- 7 are also investigated.
NASA Astrophysics Data System (ADS)
Luo, Dehai; Cha, Jing; Zhong, Linhao; Dai, Aiguo
2014-05-01
In this paper, a nonlinear multi-scale interaction (NMI) model is used to propose an eddy-blocking matching (EBM) mechanism to account for how synoptic eddies reinforce or suppress a blocking flow. It is shown that the spatial structure of the eddy vorticity forcing (EVF) arising from upstream synoptic eddies determines whether an incipient block can grow into a meandering blocking flow through its interaction with the transient synoptic eddies from the west. Under certain conditions, the EVF exhibits a low-frequency oscillation on timescales of 2-3 weeks. During the EVF phase with a negative-over- positive dipole structure, a blocking event can be resonantly excited through the transport of eddy energy into the incipient block by the EVF. As the EVF changes into an opposite phase, the blocking decays. The NMI model produces life cycles of blocking events that resemble observations. Moreover, it is shown that the eddy north-south straining is a response of the eddies to a dipole- or Ω-type block. In our model, as in observations, two synoptic anticyclones (cyclones) can attract and merge with one another as the blocking intensifies, but only when the feedback of the blocking on the eddies is included. Thus, we attribute the eddy straining and associated vortex interaction to the feedback of the intensified blocking on synoptic eddies. The results illustrate the concomitant nature of the eddy deformation, whose role as a PV source for the blocking flow becomes important only during the mature stage of a block. Our EBM mechanism suggests that an incipient block flow is amplified (or suppressed) under certain conditions by the EVF coming from the upstream of the blocking region.
Stacking with stochastic cooling
NASA Astrophysics Data System (ADS)
Caspers, Fritz; Möhl, Dieter
2004-10-01
Accumulation of large stacks of antiprotons or ions with the aid of stochastic cooling is more delicate than cooling a constant intensity beam. Basically the difficulty stems from the fact that the optimized gain and the cooling rate are inversely proportional to the number of particles 'seen' by the cooling system. Therefore, to maintain fast stacking, the newly injected batch has to be strongly 'protected' from the Schottky noise of the stack. Vice versa the stack has to be efficiently 'shielded' against the high gain cooling system for the injected beam. In the antiproton accumulators with stacking ratios up to 105 the problem is solved by radial separation of the injection and the stack orbits in a region of large dispersion. An array of several tapered cooling systems with a matched gain profile provides a continuous particle flux towards the high-density stack core. Shielding of the different systems from each other is obtained both through the spatial separation and via the revolution frequencies (filters). In the 'old AA', where the antiproton collection and stacking was done in one single ring, the injected beam was further shielded during cooling by means of a movable shutter. The complexity of these systems is very high. For more modest stacking ratios, one might use azimuthal rather than radial separation of stack and injected beam. Schematically half of the circumference would be used to accept and cool new beam and the remainder to house the stack. Fast gating is then required between the high gain cooling of the injected beam and the low gain stack cooling. RF-gymnastics are used to merge the pre-cooled batch with the stack, to re-create free space for the next injection, and to capture the new batch. This scheme is less demanding for the storage ring lattice, but at the expense of some reduction in stacking rate. The talk reviews the 'radial' separation schemes and also gives some considerations to the 'azimuthal' schemes.
Nonlinear interaction between a pair of oblique modes in a supersonic mixing layer: Long-wave limit
NASA Technical Reports Server (NTRS)
Balsa, Thomas F.; Gartside, James
1995-01-01
The nonlinear interaction between a pair of symmetric, oblique, and spatial instability modes is studied in the long-wave limit using asymptotic methods. The base flow is taken to be a supersonic mixing layer whose Mach number is such that the corresponding vortex sheet is marginally stable according to Miles' criterion. It is shown that the amplitude of the mode obeys a nonlinear integro-differential equation. Numerical solutions of this equation show that, when the obliqueness angle is less than pi/4, the effect of the nonlinearity is to enhance the growth rate of the instability. The solution terminates in a singularity at a finite streamwise location. This result is reminiscent of that obtained in the vicinity of the neutral point by other authors in several different types of flows. On the other hand, when the obliqueness angle is more than pi/4, the streamwise development of the amplitude is characterized by a series of modulations. This arises from the fact that the nonlinear term in the amplitude equation may be either stabilizing or destabilizing, depending on the value of the streamwise coordinate. However, even in this case the amplitude of the disturbance increases, though not as rapidly as in the case for which the angle is less than pi/4. Quite generally then, the nonlinear interaction between two oblique modes in a supersonic mixing layer enhances the growth of the disturbance.
NASA Astrophysics Data System (ADS)
Wang, Lei; Zhu, Yu-Jie; Wang, Zi-Qi; Xu, Tao; Qi, Feng-Hua; Xue, Yu-Shan
2016-02-01
We study the nonlinear localized waves on constant backgrounds of the Hirota-Maxwell-Bloch (HMB) system arising from the erbium doped fibers. We derive the asymmetric breather, rogue wave (RW) and semirational solutions of the HMB system. We show that the breather and RW solutions can be converted into various soliton solutions. Under different conditions of parameters, we calculate the locus of the eigenvalues on the complex plane which converts the breathers or RWs into solitons. Based on the second-order solutions, we investigate the interactions among different types of nonlinear waves including the breathers, RWs and solitons.
NASA Astrophysics Data System (ADS)
Dorfman, S.; Carter, T. A.
2015-05-01
The nonlinear three-wave interaction process at the heart of the parametric decay process is studied by launching counter-propagating Alfvén waves from antennas placed at either end of the Large Plasma Device [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)]. A resonance in the beat wave response produced by the two launched Alfvén waves is observed and is identified as a damped ion acoustic mode based on the measured dispersion relation. Other properties of the interaction including the spatial profile of the beat mode and response amplitude are also consistent with theoretical predictions for a three-wave interaction driven by a nonlinear ponderomotive force. A simple damped, driven oscillator model making use of the MHD equations well-predicts most of the observations, but the width of the resonance curve is still under investigation.
Dorfman, S.; Carter, T. A.
2015-05-15
The nonlinear three-wave interaction process at the heart of the parametric decay process is studied by launching counter-propagating Alfvén waves from antennas placed at either end of the Large Plasma Device [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)]. A resonance in the beat wave response produced by the two launched Alfvén waves is observed and is identified as a damped ion acoustic mode based on the measured dispersion relation. Other properties of the interaction including the spatial profile of the beat mode and response amplitude are also consistent with theoretical predictions for a three-wave interaction driven by a nonlinear ponderomotive force. A simple damped, driven oscillator model making use of the MHD equations well-predicts most of the observations, but the width of the resonance curve is still under investigation.
Nonlinear evolution of interacting oblique waves on two-dimensional shear layers
NASA Technical Reports Server (NTRS)
Goldstein, M. E.; Choi, S.-W.
1989-01-01
The effects of critical layer nonlinearity are considered on spatially growing oblique instability waves on nominally two-dimensional shear layers between parallel streams. The analysis shows that three-dimensional effects cause nonlinearity to occur at much smaller amplitudes than it does in two-dimensional flows. The nonlinear instability wave amplitude is determined by an integro-differential equation with cubic type nonlinearity. The numerical solutions to this equation are worked out and discussed in some detail. The numerical solutions always end in a singularity at a finite downstream distance.
Nonlinear Modeling of Dynamic Interactions within Neuronal Ensembles using Principal Dynamic Modes
Marmarelis, V. Z.; Shin, D. C.; Song, D.; Hampson, R. E.; Deadwyler, S.; Berger, T. W.
2012-01-01
A methodology for nonlinear modeling of multi-input multi-output (MIMO) neuronal systems is presented that utilizes the concept of Principal Dynamic Modes (PDM). The efficacy of this new methodology is demonstrated in the study of the dynamic interactions between neuronal ensembles in the Pre-Frontal Cortex (PFC) of a behaving non-human primate (NHP) performing a Delayed Match-to-Sample task. Recorded spike trains from Layer-2 and Layer-5 neurons were viewed as the “inputs” and “outputs”, respectively, of a putative MIMO system/model that quantifies the dynamic transformation of multi-unit neuronal activity between Layer-2 and Layer-5 of the PFC. Model prediction performance was evaluated by means of computed Receiver Operating Characteristic (ROC) curves. The PDM-based approach seeks to reduce the complexity of MIMO models of neuronal ensembles in order to enable the practicable modeling of large-scale neural systems incorporating hundreds or thousands of neurons, which is emerging as a preeminent issue in the study of neural function. The “scaling-up” issue has attained critical importance as multi-electrode recordings are increasingly used to probe neural systems and advance our understanding of integrated neural function. The initial results indicate that the PDM-based modeling methodology may greatly reduce the complexity of the MIMO model without significant degradation of performance. Furthermore, the PDM-based approach offers the prospect of improved biological/physiological interpretation of the obtained MIMO models. PMID:23011343
Bell, Iris R.; Ives, John A.; Jonas, Wayne B.
2014-01-01
Researchers are increasingly focused on the nanoscale level of organization where biological processes take place in living systems. Nanoparticles (NPs, e.g., 1–100 nm diameter) are small forms of natural or manufactured source material whose properties differ markedly from those of the respective bulk forms of the “same” material. Certain NPs have diagnostic and therapeutic uses; some NPs exhibit low-dose toxicity; other NPs show ability to stimulate low-dose adaptive responses (hormesis). Beyond dose, size, shape, and surface charge variations of NPs evoke nonlinear responses in complex adaptive systems. NPs acquire unique size-dependent biological, chemical, thermal, optical, electromagnetic, and atom-like quantum properties. Nanoparticles exhibit high surface adsorptive capacity for other substances, enhanced bioavailability, and ability to cross otherwise impermeable cell membranes including the blood-brain barrier. With super-potent effects, nano-forms can evoke cellular stress responses or therapeutic effects not only at lower doses than their bulk forms, but also for longer periods of time. Interactions of initial effects and compensatory systemic responses can alter the impact of NPs over time. Taken together, the data suggest the need to downshift the dose-response curve of NPs from that for bulk forms in order to identify the necessarily decreased no-observed-adverse-effect-level and hormetic dose range for nanoparticles. PMID:24910581
Study on Nonlinear Theory and Code of Beam-Wave Interaction for Gyroklystron
NASA Astrophysics Data System (ADS)
Jianhua, Guo; Sheng, Yu; Xiang, Li; Hongfu, Li
2011-12-01
A nonlinear self-consistent theory of beam-wave interaction for gyroklystron with multiple cavities is analyzed in this paper. The electron motion equations and transient electromagnetic field equations in a complex form are deduced in detail. A calculation code including a time-dependent description of the electromagnetic fields and a self-consistent analysis of the electrons is designed and the corresponding software implementation is achieved using Fortran language. An example is presented for the operation of the code, namely a four-cavity, Ka-band gyroklystron operating in the TE011 mode at the fundamental of the cyclotron frequency. The numerical results show that a maximal saturated peak output power of 330 kW, corresponding to 39% efficiency and a saturated 3-dB bandwidth of 325 MHz is achieved with a 72.8 kv, 11.8 A electron beam at a focused magnetic field of 13 kG and a beam velocity ratio of 1.63 when the speed spread is 5%. By comparison, the numerical results agree with the experimental results.
NASA Astrophysics Data System (ADS)
Nagatomo, Makoto; Kaya, Nobuyuki; Matsumoto, Hiroshi
The Microwave Ionosphere Nonlinear Interaction Experiment (MINIX) is a sounding rocket experiment to study possible effects of strong microwave fields in case it is used for energy transmission from the Solar Power Satellite (SPS) upon the Earth's atmosphere. Its secondary objective is to develop high power microwave technology for space use. Two rocket-borne magnetrons were used to emit 2.45 GHz microwave in order to make a simulated condition of power transmission from an SPS to a ground station. Sounding of the environment radiated by microwave was conducted by the diagnostic package onboard the daughter unit which was separated slowly from the mother unit. The main design drivers of this experiment were to build such high power equipments in a standard type of sounding rocket, to keep the cost within the budget and to perform a series of experiments without complete loss of the mission. The key technology for this experiment is a rocket-borne magnetron and high voltage converter. Location of position of the daughter unit relative to the mother unit was a difficult requirement for a spin-stabilized rocket. These problems were solved by application of such a low cost commercial products as a magnetron for microwave oven and a video tape recorder and camera.
NASA Technical Reports Server (NTRS)
Cain, A. B.; Thompson, M. W.
1986-01-01
The growth of the momentum thickness and the modal disturbance energies are examined to study the nature and onset of nonlinearity in a temporally growing free shear layer. A shooting technique is used to find solutions to the linearized eigenvalue problem, and pseudospectral weakly nonlinear simulations of this flow are obtained for comparison. The roll-up of a fundamental disturbance follows linear theory predictions even with a 20 percent disturbance amplitude. A weak nonlinear interaction of the disturbance creates a finite-amplitude mean shear stress which dominates the growth of the layer momentum thickness, and the disturbance growth rate changes until the fundamental disturbance dominates. The fundamental then becomes an energy source for the harmonic, resulting in an increase in the growth rate of the subharmonic over the linear prediction even when the fundamental has no energy to give. Also considered are phase relations and the wall influence.
Stacking Global Seismograms Revisited
NASA Astrophysics Data System (ADS)
Shearer, P. M.; Buehler, J. S.; Denolle, M.; Fan, W.; Ma, Z.; Mancinelli, N. J.; Matoza, R. S.; Wang, W.; Wang, Y.; Zhan, Z.
2014-12-01
Over 20 years ago, stacks of global seismograms produced direct images of the global seismic wavefield highlighting the visibility, frequency content, and polarity of known seismic phases, and also identified a host of new phases associated with reflections and phase conversions from upper-mantle discontinuities. Two different stacking methods proved particularly useful: (1) STA/LTA-filtered stacks that describe the local signal-to-noise characteristics of the major seismic phases. These serve to image the entire wavefield in a uniform way for educational purposes and to show which phases are observed most clearly as a guide to future research. These stacks also resolve SH versus SV timing differences consistent with radial anisotropy. (2) Reference-phase stacks that preserve the polarity, amplitude, and timing of traces with respect to a specified target phase. These show a large number of top-side and bottom-side reflections and phase conversions from the 410- and 660-km discontinuities that create weak phases with a characteristic "railroad track" appearance both preceding and following many of the main seismic phases. Reference-phase stacking can also be used to produce coherent surface-wave stacks at very long periods, which directly show the dispersive character of the surface waves. Here we revisit and update these stacks by exploiting the vastly increased data now available from the IRIS DMC to produce greatly improved wavefield images. We present several examples of the different stacking approaches and point out their various features, including promising targets for future research.
NASA Astrophysics Data System (ADS)
Xiang, Yanxun; Deng, Mingxi; Xuan, Fu-Zhen; Liu, Chang-Jun
2012-05-01
An analytical model is presented for the effect of the interactions of dislocations with precipitate coherency strains on the generation of second-harmonic of Lamb waves in metallic alloys. The cumulative second-harmonic of Lamb wave propagation is shown to depend dominantly on the dislocation density, pinning dislocation length, internal stress due to the coherency strain, volume fraction of the precipitates, and the phase matching degree between the primary Lamb wave and the double frequency Lamb wave (DFLW). Experiments were carried out to introduce controlled levels of creep-induced damage to determine the nonlinear response of Lamb waves in titanium alloy Ti60 plates. A like mountain-shape change in the normalized acoustic nonlinearity of Lamb wave versus the creep loading time has been observed. Microscopic image analyses were performed to interpret the variation of the measured acoustic nonlinearity and to obtain the microstructure parameters of the Ti60 specimens with different creep damages. The analytical model was applied to these creep damaged Ti60 specimens, which revealed a good accordance with the measured results of the nonlinear Lamb waves. These results indicate that the acoustic nonlinearity of Lamb wave increases due to the rising of the precipitation volume fraction and the dislocation density in the early stage, and it decreases as a combined result of the reduction of the precipitation volume fraction and the dislocation density and the increasing mismatch of the phase velocity between the primary Lamb wave and the DFLW after a further creep loading.
Bravaya, Ksenia B.; Kostko, Oleg; Ahmed, Musahid; Krylov, Anna I.
2009-09-02
A combined theoretical and experimental study of the ionized dimers of thymine and adenine, TT, AA, and AT, is presented. Adiabatic and vertical ionization energies(IEs) for monomers and dimers as well as thresholds for the appearance of the protonated species are reported and analyzed. Non-covalent interactions stronglyaffect the observed IEs. The magnitude and the nature of the effect is different for different isomers of the dimers. The computations reveal that for TT, the largestchanges in vertical IEs (0.4 eV) occur in asymmetric h-bonded and symmetric pi- stacked isomers, whereas in the lowest-energy symmetric h-bonded dimer the shiftin IEs is much smaller (0.1 eV). The origin of the shift and the character of the ionized states is different in asymmetric h-bonded and symmetric stacked isomers. Inthe former, the initial hole is localized on one of the fragments, and the shift is due to the electrostatic stabilization of the positive charge of the ionized fragment by thedipole moment of the neutral fragment. In the latter, the hole is delocalized, and the change in IE is proportional to the overlap of the fragments' MOs. The shifts in AAare much smaller due to a less effcient overlap and a smaller dipole moment. The ionization of the h-bonded dimers results in barrierless (or nearly barrierless) protontransfer, whereas the pi-stacked dimers relax to structures with the hole stabilized by the delocalization or electrostatic interactions.
NASA Astrophysics Data System (ADS)
Neilson, Peter D.; Neilson, Megan D.
2005-09-01
Adaptive model theory (AMT) is a computational theory that addresses the difficult control problem posed by the musculoskeletal system in interaction with the environment. It proposes that the nervous system creates motor maps and task-dependent synergies to solve the problems of redundancy and limited central resources. These lead to the adaptive formation of task-dependent feedback/feedforward controllers able to generate stable, noninteractive control and render nonlinear interactions unobservable in sensory-motor relationships. AMT offers a unified account of how the nervous system might achieve these solutions by forming internal models. This is presented as the design of a simulator consisting of neural adaptive filters based on cerebellar circuitry. It incorporates a new network module that adaptively models (in real time) nonlinear relationships between inputs with changing and uncertain spectral and amplitude probability density functions as is the case for sensory and motor signals.
Study of Nonlinear Interaction and Turbulence of Alfven Waves in LAPD Experiments
Boldyrev, Stanislav; Perez, Jean Carlos
2013-11-29
The complete project had two major goals — investigate MHD turbulence generated by counterpropagating Alfven modes, and study such processes in the LAPD device. In order to study MHD turbulence in numerical simulations, two codes have been used: full MHD, and reduced MHD developed specialy for this project. Quantitative numerical results are obtained through high-resolution simulations of strong MHD turbulence, performed through the 2010 DOE INCITE allocation. We addressed the questions of the spectrum of turbulence, its universality, and the value of the so-called Kolmogorov constant (the normalization coefficient of the spectrum). In these simulations we measured with unprecedented accuracy the energy spectra of magnetic and velocity fluctuations. We also studied the so-called residual energy, that is, the difference between kinetic and magnetic energies in turbulent fluctuations. In our analytic work we explained generation of residual energy in weak MHD turbulence, in the process of random collisions of counterpropagating Alfven waves. We then generalized these results for the case of strong MHD turbulence. The developed model explained generation of residual energy is strong MHD turbulence, and verified the results in numerical simulations. We then analyzed the imbalanced case, where more Alfven waves propagate in one direction. We found that spectral properties of the residual energy are similar for both balanced and imbalanced cases. We then compared strong MHD turbulence observed in the solar wind with turbulence generated in numerical simulations. Nonlinear interaction of Alfv´en waves has been studied in the upgraded Large Plasma Device (LAPD). We have simulated the collision of the Alfven modes in the settings close to the experiment. We have created a train of wave packets with the apltitudes closed to those observed n the experiment, and allowed them to collide. We then saw the generation of the second harmonic, resembling that observed in the
Liu, Zheng; Cao, J. C.; Sanderson, Matthew; Zhang, Chao
2015-07-28
The effect of Rashba spin-orbit coupling on the nonlinear optical conductivity in a bilayer graphene is investigated. We demonstrate the very different role played by the Rashba term and interlayer hopping; in some cases, the two roles can be quite opposite. It is found that the Rashba term can either enhance or suppress the nonlinear effect in a bilayer graphene, depending on the strength of the interlayer hopping. For a weak interlayer hopping, the Rashba term can significantly enhance the nonlinear effect. An analytical result was derived, showing the interplay of the Rashba effect and the interlayer hopping effect.
Qiu, Cheng-Wei; Novitsky, Andrey; Ma, Hua; Qu, Shaobo
2009-07-01
An analytical method of electromagnetic wave interactions with a general radially anisotropic cloak is established. It is able to deal with arbitrary parameters [ epsilon r (r) , mu r (r) , epsilon t (r) , and mu t (r) ] of a radially anisotropic inhomogeneous shell. The general cloaking condition is proposed from the wave relations, in contrast to the method of transformation optics. Spherical metamaterial cloaks with improved invisibility performance are achieved with optimal nonlinearity in transformation and core-shell ratio. PMID:19658829
Reeves, Adam A.
1977-04-12
Hot stack gases transfer contained heat to a gravity flow of pebbles treated with a catalyst, cooled stacked gases and a sulfuric acid mist is withdrawn from the unit, and heat picked up by the pebbles is transferred to air for combustion or other process. The sulfuric acid (or sulfur, depending on the catalyst) is withdrawn in a recovery unit.
NASA Technical Reports Server (NTRS)
Cantrell, John H., Jr.; Cantrell, Sean A.
2008-01-01
A comprehensive analytical model of the interaction of the cantilever tip of the atomic force microscope (AFM) with the sample surface is developed that accounts for the nonlinearity of the tip-surface interaction force. The interaction is modeled as a nonlinear spring coupled at opposite ends to linear springs representing cantilever and sample surface oscillators. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a standard iteration procedure. Solutions are obtained for the phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) techniques including force modulation microscopy, atomic force acoustic microscopy, ultrasonic force microscopy, heterodyne force microscopy, resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), and the commonly used intermittent contact mode (TappingMode) generally available on AFMs. The solutions are used to obtain a quantitative measure of image contrast resulting from variations in the Young modulus of the sample for the amplitude and phase images generated by the A-AFM techniques. Application of the model to RDF-AFUM and intermittent soft contact phase images of LaRC-cp2 polyimide polymer is discussed. The model predicts variations in the Young modulus of the material of 24 percent from the RDF-AFUM image and 18 percent from the intermittent soft contact image. Both predictions are in good agreement with the literature value of 21 percent obtained from independent, macroscopic measurements of sheet polymer material.
NASA Astrophysics Data System (ADS)
Lundberg, Oskar E.; Nordborg, Anders; Lopez Arteaga, Ines
2016-03-01
A state-dependent contact model including nonlinear contact stiffness and nonlinear contact filtering is used to calculate contact forces and rail vibrations with a time-domain wheel-track interaction model. In the proposed method, the full three-dimensional contact geometry is reduced to a point contact in order to lower the computational cost and to reduce the amount of required input roughness-data. Green's functions including the linear dynamics of the wheel and the track are coupled with a point contact model, leading to a numerically efficient model for the wheel-track interaction. Nonlinear effects due to the shape and roughness of the wheel and the rail surfaces are included in the point contact model by pre-calculation of functions for the contact stiffness and contact filters. Numerical results are compared to field measurements of rail vibrations for passenger trains running at 200 kph on a ballast track. Moreover, the influence of vehicle pre-load and different degrees of roughness excitation on the resulting wheel-track interaction is studied by means of numerical predictions.
Nonlinear interaction of infrared waves on a VO2 surface at a semiconductor-metal phase transition
NASA Astrophysics Data System (ADS)
Berger, N. K.; Zhukov, E. A.; Novokhatskii, V. V.
1984-04-01
Nonlinear interactions (including wavefront reversal) of light from CW or pulsed 10.6-micron CO2 lasers at the semiconductor-metal phase transition in a VO2 film are investigated experimentally. The results are presented in graphs and characterized in detail. The intensity reflection coefficients of the three-wave interactions are found to be 0.5 percent for a CW reference wave of intensity 900 mW/sq cm and 42 percent for a pulsed reference wave of threshold density 600-800 microjoule/sq cm.
N-soliton interactions in an extended Schrödinger equation with higher order of nonlinearities
NASA Astrophysics Data System (ADS)
Yomba, Emmanuel; Zakeri, Gholam-Ali
2016-02-01
We investigate the existence of N-solitons in an extended general nonlinear Schrödinger equation with third and fourth order dispersive terms that is most important for applications, such as the dynamics of a general class of anisotropic Heisenberg ferromagnetic spin chain with different magnetic interactions, the alpha helical proteins, and in media that offer interactions in biophysics. We have transformed the model to a homogeneous model that is utilized to show the existence of interactions of N-soliton solutions. We analyzed, and gave specific forms of these new class of N-solitons in a new simple form and discussed the interactions of these N-solitons. We have shown the existence of three types of head-on collisions, head-on collisions with or without over-taking or splitting into two solitons.
Han, Jiu-Ning Luo, Jun-Hua; Li, Jun-Xiu; Li, Sheng-Chang; Liu, Shi-Wei; Yang, Yang; Duan, Wen-Shan; Han, Juan-Fang
2015-06-15
We study the basic physical properties of composite nonlinear structure induced by the head-on collision of magnetosonic solitons. Solitary waves are assumed to propagate in a quantum electron-ion magnetoplasma with spin-1/2 degenerate electrons. The main interest of the present work is to investigate the time evolution of the merged composite structure during a specific time interval of the wave interaction process. We consider three cases of colliding-situation, namely, compressive-rarefactive solitons interaction, compressive-compressive solitons interaction, and rarefactive-rarefactive solitons interaction, respectively. Compared with the last two colliding cases, the changing process of the composite structure is more complex for the first situation. Moreover, it is found that they are obviously different for the last two colliding cases.
Nichols, Zachary; Nirenberg, Sheila
2013-01-01
The early visual system is a model for understanding the roles of cell populations in parallel processing. Cells in this system can be classified according to their responsiveness to different stimuli; a prominent example is the division between cells that respond to stimuli of opposite contrasts (ON vs OFF cells). These two cell classes display many asymmetries in their physiological characteristics (including temporal characteristics, spatial characteristics, and nonlinear characteristics) that, individually, are known to have important roles in population coding. Here we describe a novel distinction between the information that ON and OFF ganglion cell populations carry in mouse—that OFF cells are able to signal motion information about both light and dark objects, while ON cells have a selective deficit at signaling the motion of dark objects. We found that none of the previously reported asymmetries in physiological characteristics could account for this distinction. We therefore analyzed its basis via a recently developed linear–nonlinear-Poisson model that faithfully captures input/output relationships for a broad range of stimuli (Bomash et al., 2013). While the coding differences between ON and OFF cell populations could not be ascribed to the linear or nonlinear components of the model individually, they had a simple explanation in the way that these components interact. Sensory transformations in other systems can likewise be described by these models, and thus our findings suggest that similar interactions between component properties may help account for the roles of cell classes in population coding more generally. PMID:24027295
Romera, M.; Monteblanco, E.; Garcia-Sanchez, F.; Buda-Prejbeanu, L. D.; Ebels, U.; Delaët, B.
2015-05-11
The influence of dynamic coupling in between magnetic layers of a standard spin torque nano-oscillator composed of a synthetic antiferromagnet (SyF) as a polarizer and an in-plane magnetized free layer has been investigated. Experiments on spin valve nanopillars reveal non-continuous features such as kinks in the frequency field dependence that cannot be explained without such interactions. Comparison of experiments to numerical macrospin simulations shows that this is due to non-linear interaction between the spin torque (STT) driven mode and a damped mode that is mediated via the third harmonics of the STT mode. It only occurs at large applied currents and thus at large excitation amplitudes of the STT mode. Under these conditions, a hybridized mode characterized by a strong reduction of the linewidth appears. The reduced linewidth can be explained by a reduction of the non-linear contribution to the linewidth via an enhanced effective damping. Interestingly, the effect depends also on the exchange interaction within the SyF. An enhancement of the current range of reduced linewidth by a factor of two and a reduction of the minimum linewidth by a factor of two are predicted from simulation when the exchange interaction strength is reduced by 30%. These results open directions to optimize the design and microwave performances of spin torque nano-oscillators taking advantage of the coupling mechanisms.
Higher order harmonic detection for exploring nonlinear interactions with nanoscale resolution
Vasudevan, R. K.; Okatan, M. Baris; Rajapaksa, I.; Kim, Y.; Marincel, D.; Trolier-McKinstry, S.; Jesse, S.; Valanoor, N.; Kalinin, S. V.
2013-01-01
Nonlinear dynamics underpin a vast array of physical phenomena ranging from interfacial motion to jamming transitions. In many cases, insight into the nonlinear behavior can be gleaned through exploration of higher order harmonics. Here, a method using band excitation scanning probe microscopy (SPM) to investigate higher order harmonics of the electromechanical response, with nanometer scale spatial resolution is presented. The technique is demonstrated by probing the first three harmonics of strain for a Pb(Zr1-xTix)O3 (PZT) ferroelectric capacitor. It is shown that the second order harmonic response is correlated with the first harmonic response, whereas the third harmonic is not. Additionally, measurements of the second harmonic reveal significant deviations from Rayleigh-type models in the form of a much more complicated field dependence than is observed in the spatially averaged data. These results illustrate the versatility of nth order harmonic SPM detection methods in exploring nonlinear phenomena in nanoscale materials. PMID:24045269
Nonlinear relativistic interaction of an ultrashort laser pulse with a cold plasma
Rax, J.M.; Fisch, N.J.
1992-01-01
We investigate the nonlinear, relativistic dynamics that result when intense (10{sup 18}W/cm{sup 2} and above) and ultrashort (one plasma period or shorter) laser pulse travels through a cold underdense plasma. Using a Lagrangian analysis of the plasma response, it can be demonstrated that the nonlinear wake, the collective dissipation, the nonlinear Compton losses, and the harmonic generation, are all determined by a finite set of integrated scalar quantities. This result holds for one-dimensional, short pulses of arbitrary amplitude, shape, and polarization, so that these very short intense laser pulses in a plasma can be viewed essentially as a quasiparticle characterized by a small set of global parameters.
NASA Technical Reports Server (NTRS)
Liepmann, H. W.; Torczynski, J. R.
1983-01-01
Second sound techniques were used to study superfluid helium. Second sound shock waves produced relative velocities in the bulk fluid. Maximum counterflow velocities produced in this way are found to follow the Langer-Fischer prediction for the fundamental critical velocity in its functional dependence on temperature and pressure. Comparison of successive shock and rotating experiments provides strong evidence that breakdown results in vorticity production in the flow behind the shock. Schlieren pictures have verified the planar nature of second sound shocks even after multiple reflections. The nonlinear theory of second sound was repeatedly verified in its prediction of double shocks and other nonlinear phenomena.
Energy Science and Technology Software Center (ESTSC)
2007-08-22
The pamtest utility calls the normal PAM hooks using a service and username supplied on the command line. This allows an administratory to test any one of many configured PAM stacks as any existing user on the machine.
NASA Technical Reports Server (NTRS)
Ohnami, S.; Hayakawa, M.; Bell, T. F.; Ondoh, T.
1993-01-01
Nonlinear wave-wave interaction between signals from a ground-based VLF transmitter and narrow-band ELF emissions in the subauroral ionosphere is studied by means of the bispectrum and bicoherence analysis. A bicoherence analysis has indicated that the sideband structures around the Siple transmitter signal received onboard the ISIS satellite are due to the nonlinear interaction between the Siple VLF signal and the pre-existing ELF emission.
Fuerst, J.D.; /Fermilab
1988-01-22
There are two nitrogen/argon exhaust headers in the D0 cryogenic piping system, one for the liquid argon dewar and another for the three argon calorimeters. These headers serve two functions, venting both nitrogen exhaust from the cooling loops and cold argon gas should any argon vessel blow a relief. These headers are vacuum jacketed until they exit the building. At that point, uninsulated exhaust stacks direct the flow into the atmosphere. This note deals with the these stacks.
NASA Astrophysics Data System (ADS)
Claeys, M.; Sinou, J.-J.; Lambelin, J.-P.; Todeschini, R.
2016-08-01
The nonlinear vibration response of an assembly with friction joints - named "Harmony" - is studied both experimentally and numerically. The experimental results exhibit a softening effect and an increase of dissipation with excitation level. Modal interactions due to friction are also evidenced. The numerical methodology proposed groups together well-known structural dynamic methods, including finite elements, substructuring, Harmonic Balance and continuation methods. On the one hand, the application of this methodology proves its capacity to treat a complex system where several friction movements occur at the same time. On the other hand, the main contribution of this paper is the experimental and numerical study of evidence of modal interactions due to friction. The simulation methodology succeeds in reproducing complex form of dynamic behavior such as these modal interactions.
Cross-polarized wave generation by effective cubic nonlinear optical interaction.
Petrov, G I; Albert, O; Etchepare, J; Saltiel, S M
2001-03-15
A new cubic nonlinear optical effect in which a linearly polarized wave propagating in a single quadratic medium is converted into a wave that is cross polarized to the input wave is observed in BBO crystal. The effect is explained by cascading of two different second-order processes: second-harmonic generation and difference frequency mixing. PMID:18040322
Effects of focusing on third-order nonlinear processes in isotropic media. [laser beam interactions
NASA Technical Reports Server (NTRS)
Bjorklund, G. C.
1975-01-01
Third-order nonlinear processes in isotropic media have been successfully used for tripling the efficiency of high-power laser radiation for the production of tunable and fixed-frequency coherent vacuum UV radiation and for up-conversion of IR radiation. The effects of focusing on two processes of this type are studied theoretically and experimentally.
Exactly solvable model for nonlinear light-matter interaction in an arbitrary time-dependent field
Brown, J. M.; Lotti, A.; Teleki, A.; Kolesik, M.
2011-12-15
Exact analytic expressions are derived for the dipole moment and nonlinear current of a one-dimensional quantum particle subject to a short-range attractive potential and an arbitrary time-dependent electric field. An efficient algorithm for the current evaluation is described and a robust implementation suitable for numerical simulations is demonstrated.
Sproll, Markus; Noske, Matthias; Kammerer, Matthias; Dieterle, Georg; Weigand, Markus; Stoll, Hermann; Schütz, Gisela; Bauer, Hans; Gangwar, Ajay; Woltersdorf, Georg; Back, Christian H.
2014-01-06
We show, by experiments and micromagnetic simulations in vortex structures, that an active “dual frequency” excitation of both the sub-GHz vortex gyromode and multi-GHz spin waves considerably changes the frequency response of spin wave mediated vortex core reversal. Besides additional minima in the switching threshold, a significant broadband reduction of the switching amplitudes is observed, which can be explained by non-linear interaction between the vortex gyromode and the spin waves. We conclude that the well known frequency spectra of azimuthal spin waves in vortex structures are altered substantially, when the vortex gyromode is actively excited simultaneously.
Chen, H.W.; Aine, C.J.; Flynn, E.R.; Wood, C.C.
1996-02-01
Reciprocal connections, in essence, are the dynamic wiring (connections) of the neural network circuitry. Given the high complexity of the neural circuitry in the human brain, it is quite a challenge to study the dynamic wiring of highly parallel and widely distributed neural networks. The measurements of stimulus evoked coherent oscillations provide indirect evidence of dynamic wiring. In this study, in addition to the coherent oscillation measurements, two more techniques are discussed for testing possible dynamic wiring: measurements of spatio-temporal interactions beyond the classical receptive fields, and neural structural testing using nonlinear systems analysis.
Mukamel, Shaul
2016-07-28
Nonlinear spectroscopy signals detected by fluorescence from dilute samples of N non-interacting molecules are usually adequately described by simply multiplying the single molecule response by N. We show that signals that scale with higher powers of N are generated by the joint detection of several particles. This can be accomplished by phase sensitive detection such as phase cycling, photo-acoustic modulation, or by Hanbury-Brown Twiss photon coincidence. Such measurements can dissect the ensemble according to the number of excited particles. PMID:27475341
NASA Astrophysics Data System (ADS)
Mukamel, Shaul
2016-07-01
Nonlinear spectroscopy signals detected by fluorescence from dilute samples of N non-interacting molecules are usually adequately described by simply multiplying the single molecule response by N. We show that signals that scale with higher powers of N are generated by the joint detection of several particles. This can be accomplished by phase sensitive detection such as phase cycling, photo-acoustic modulation, or by Hanbury-Brown Twiss photon coincidence. Such measurements can dissect the ensemble according to the number of excited particles.
NASA Astrophysics Data System (ADS)
Khadzhi, P. I.; Lyakhomskaya, K. D.; Nadkin, L. Y.; Markov, D. A.
2002-05-01
The characteristic peculiarities of the self-reflection of a strong electromagnetic wave in a system of coherent excitons and biexcitons due to the exciton-photon interaction and optical exciton-biexciton conversion in semiconductors were investigated as one of the manifestations of nonlinear optical Stark-effect. It was found that a monotonously decreasing standing wave with an exponential decreasing spatial tail is formed in the semiconductor. Under the action of the field of a strong pulse, an optically homogeneous medium is converted, into the medium with distributed feedback. The appearance of the spatially separated narrow pears of the reflective index, extinction and reflection coefficients is predicted.
NASA Astrophysics Data System (ADS)
Berger, N. K.; Zhukov, E. A.; Novokhatskiĭ, V. V.
1984-04-01
The use of a semiconductor-metal phase transition for wavefront reversal of laser radiation was proposed. An investigation was made of nonlinear reflection of CO2 laser radiation at a phase transition in VO2. A three-wave interaction on a VO2 surface was achieved using low-power cw and pulsed CO2 lasers. In the first case, the intensity reflection coefficient was 0.5% for a reference wave intensity of 0.9 W/cm2 and in the second case, it was 42% for a threshold reference wave energy density of 0.6-0.8 mJ/cm2.
NASA Astrophysics Data System (ADS)
Buron, J. D.; Houde, S.; Lestriez, R.; Deschênes, C.
2015-01-01
Steady state and non-linear harmonic (NLH) flow simulations were performed within the framework of the Francis-99 project in order to assess the capacity of the NLH method to capture the main pressure fluctuations associated with the rotor-stator interactions between the distributor and the runner of the turbine. This paper focusses on the methodology developed to obtain harmonic solutions and presents preliminary results from the simulations using the flow solver NUMECA FineTURBO on intermediate grid level meshes. Comparisons of the first simulations to experimental data reveal good agreement concerning the predicted pressure amplitudes notably at high load operating condition.
NASA Astrophysics Data System (ADS)
Yang, K. F.; Liu, H. W.; Nagase, K.; Amakata, K.; Mishima, T. D.; Santos, M. B.; Hirayama, Y.
2011-12-01
We measure the spin polarization (P) of two-dimensional electron gases confined to an InSb quantum well using parallel and tilted magnetic fields. The nonlinear field dependence of P is prominent, leading to a direct deduction of the spin susceptibility (χs) over a wide range of P from 0.07 to 1. χs is found to increase nonlinearly with P and exceed χgm ∝ m*g* (where m* and g* are the effective mass and g factor) as commonly used in experiments. We show that χs and χgm obey a square law χs/χ0 = (χgm/χ0)2, where χ0 is the paramagnetic spin susceptibility.
Nonlinear elastic wave interaction in a sandstone bar: A summary of recent pulse-mode experiments
Johnson, P.A.; TenCate, J.A.; Cherry, R.; McCall, K.; Van Den Abeele, K.; Kadish, A.; Shankland, T.; Guyer, R. |
1995-03-01
We have performed nonlinear pulse propagation experiments in a 3.8 cm diameter rod of Berea sandstone 1.8 m long at ambient conditions. Unlike earlier studies, we measured acceleration and not displacement. Moreover, we detected 2nd and 3rd harmonic growth at smaller strain amplitudes than were observed previously (10{sup {minus}7}). Harmonic growth at identical strain amplitudes has also been noted in resonance studies using the same rock type. Current measurements are underway with the rod in vacuum where the wave attenuation is less and the conditions can be carefully controlled. Ultimately, we wish to test the validity of current analytic and numerical models for nonlinear propagation in microcracked materials.
Observation of Quasi-Two-Dimensional Nonlinear Interactions in a Drift-Wave Streamer
Yamada, T.; Nagashima, Y.; Itoh, S.-I.; Inagaki, S.; Kamataki, K.; Yagi, M.; Fujisawa, A.; Kasuya, N.; Itoh, K.; Arakawa, H.; Kobayashi, T.
2010-11-26
A streamer, which is a bunching of drift-wave fluctuations, and its mediator, which generates the streamer by coupling with other fluctuations, have been observed in a cylindrical magnetized plasma. Their radial structures were investigated in detail by using the biphase analysis. Their quasi-two-dimensional structures were revealed to be equivalent with a pair of fast and slow modes predicted by a nonlinear Schroedinger equation based on the Hasegawa-Mima model.
Wave-particle interaction and the nonlinear saturation of the electron temperature gradient mode
NASA Astrophysics Data System (ADS)
Vadlamani, Srinath; Parker, Scott E.; Chen, Yang; Howard, James E.
2004-11-01
It has been proposed that the electron temperature gradient (ETG) driven turbulence is responsible for experimentally relevant electron thermal transport in tokamak plasmas. Significant transport levels are possible by the creation of radially elongated vortices or ``streamers" [1,2], which are sustained by the nonlinear saturation of the instability and are not susceptible to shear flow destruction, as is the case with the ion temperature gradient (ITG) mode. We present a dynamical system to explore the dependence of saturation level due to E × B and E_\\| motion, as well as the effect of radial elongation. With this model, we can predict the nonlinear saturation level of the ETG streamers. We compare our theoretical predictions with a 2D shear-less slab gyrokinetic electron code that includes the E_\\| nonlinearity. [1]F. Jenko, W. Dorland, M Kotschenreuther, and B.N. Rogers, Phys. Plasmas 7, 1904 (2000). [2]C. Holland, and P.H. Diamond, Phys. Plasmas 9, 3857 (2002). [3]W. M. Manheimer, Phys. Fluids 14, 579 (1971). [4]R. A. Smith, John A. Krommes, and W. W. Lee, Phys. Fluids 28, 1069 (1985).
NASA Astrophysics Data System (ADS)
Zhang, Yunge; Zhang, Dongdong; Cai, Minghan; Li, Yilang; Zhang, Deqiang; Qiu, Yong; Duan, Lian
2016-03-01
Thermally activated delayed fluorescence (TADF) materials have attracted much attention as they can achieve 100% theoretical internal quantum efficiency without using expensive noble metals. However, efficient red TADF emitters are hard to realize according to the energy gap law. Here, three donor-acceptor-donor type TADF emitters with the same acceptor of o-phthalodinitrile (PN) but different donors (9, 9-dimethyl-9, 10-dihydroacridine (DMAC), phenoxazine (PXZ), and phenothiazine (PTZ) for DMAC-PN, PXZ-PN, and PTZ-PN, respectively) have been synthesized, and it is observed that the performance of the emitters can be improved by reducing the intra-molecular π-π stacking. DMAC-PN with reduced intra-molecular π-π stacking shows a photoluminescence quantum yield (PLQY) of 20.2% in degassed toluene solution, much higher than those of PXZ-PN, and PTZ-PN (0.8%, 0.2%, respectively). An organic light-emitting diode (OLED) employing DMAC-PN doped into 4,4‧-bis(9H-carbazol-9-yl)biphenyl (CBP) as the emitting layer exhibits a maximum external quantum efficiency (EQE) of 10.2% with the emission peak at 564 nm. Moreover, when DMAC-PN is doped into a polar host, bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO), the OLED shows a large redshift of the emission maximum to 594 nm, while maintaining a peak EQE as high as 7.2%, indicating that efficient red TADF OLEDs can be fabricated by doping orange TADF emitters into hosts with proper polarity.
Zhang, Yunge; Zhang, Dongdong; Cai, Minghan; Li, Yilang; Zhang, Deqiang; Qiu, Yong; Duan, Lian
2016-03-01
Thermally activated delayed fluorescence (TADF) materials have attracted much attention as they can achieve 100% theoretical internal quantum efficiency without using expensive noble metals. However, efficient red TADF emitters are hard to realize according to the energy gap law. Here, three donor-acceptor-donor type TADF emitters with the same acceptor of o-phthalodinitrile (PN) but different donors (9, 9-dimethyl-9, 10-dihydroacridine (DMAC), phenoxazine (PXZ), and phenothiazine (PTZ) for DMAC-PN, PXZ-PN, and PTZ-PN, respectively) have been synthesized, and it is observed that the performance of the emitters can be improved by reducing the intra-molecular π-π stacking. DMAC-PN with reduced intra-molecular π-π stacking shows a photoluminescence quantum yield (PLQY) of 20.2% in degassed toluene solution, much higher than those of PXZ-PN, and PTZ-PN (0.8%, 0.2%, respectively). An organic light-emitting diode (OLED) employing DMAC-PN doped into 4,4'-bis(9H-carbazol-9-yl)biphenyl (CBP) as the emitting layer exhibits a maximum external quantum efficiency (EQE) of 10.2% with the emission peak at 564 nm. Moreover, when DMAC-PN is doped into a polar host, bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO), the OLED shows a large redshift of the emission maximum to 594 nm, while maintaining a peak EQE as high as 7.2%, indicating that efficient red TADF OLEDs can be fabricated by doping orange TADF emitters into hosts with proper polarity. PMID:26821694
Porter, Reid B; Hush, Don
2009-01-01
Just as linear models generalize the sample mean and weighted average, weighted order statistic models generalize the sample median and weighted median. This analogy can be continued informally to generalized additive modeels in the case of the mean, and Stack Filters in the case of the median. Both of these model classes have been extensively studied for signal and image processing but it is surprising to find that for pattern classification, their treatment has been significantly one sided. Generalized additive models are now a major tool in pattern classification and many different learning algorithms have been developed to fit model parameters to finite data. However Stack Filters remain largely confined to signal and image processing and learning algorithms for classification are yet to be seen. This paper is a step towards Stack Filter Classifiers and it shows that the approach is interesting from both a theoretical and a practical perspective.
Chou, W.; Wildman, D.; Zheng, H.; Takagi, A.; /KEK, Tsukuba
2004-12-01
A novel wideband RF system, nicknamed the barrier RF, has been designed, fabricated and installed in the Fermilab Main Injector. The cavity is made of seven Finemet cores, and the modulator made of two bipolar high-voltage fast solid-state switches. The system can deliver {+-}7 kV square pulses at 90 kHz. The main application is to stack two proton batches injected from the Booster and squeeze them into the size of one so that the bunch intensity can be doubled. High intensity beams have been successfully stacked and accelerated to 120 GeV with small losses. The problem of large longitudinal emittance growth is the focus of the present study. An upgraded system with two barrier RF cavities for continuous stacking is under construction. This work is part of the US-Japan collaborative agreement.
Chou, W.; Wildman, D.; Zheng, H.; Takagi, A.
2005-06-08
A novel wideband RF system, nicknamed the barrier RF, has been designed, fabricated and installed in the Fermilab Main Injector. The cavity is made of seven Finemet cores, and the modulator made of two bipolar high-voltage fast solid-state switches. The system can deliver {+-}7 kV square pulses at 90 kHz. The main application is to stack two proton batches injected from the Booster and squeeze them into the size of one so that the bunch intensity can be doubled. High intensity beams have been successfully stacked and accelerated to 120 GeV with small losses. The problem of large longitudinal emittance growth is the focus of the present study. An upgraded system with two barrier RF cavities for continuous stacking is under construction. This work is part of the US-Japan collaborative agreement.
NASA Astrophysics Data System (ADS)
Chou, W.; Wildman, D.; Zheng, H.; Takagi, A.
2005-06-01
A novel wideband RF system, nicknamed the barrier RF, has been designed, fabricated and installed in the Fermilab Main Injector. The cavity is made of seven Finemet cores, and the modulator made of two bipolar high-voltage fast solid-state switches. The system can deliver ±7 kV square pulses at 90 kHz. The main application is to stack two proton batches injected from the Booster and squeeze them into the size of one so that the bunch intensity can be doubled. High intensity beams have been successfully stacked and accelerated to 120 GeV with small losses. The problem of large longitudinal emittance growth is the focus of the present study. An upgraded system with two barrier RF cavities for continuous stacking is under construction. This work is part of the US-Japan collaborative agreement.
NASA Astrophysics Data System (ADS)
Banks, J. W.; Henshaw, W. D.; Kapila, A. K.; Schwendeman, D. W.
2016-01-01
We describe an added-mass partitioned (AMP) algorithm for solving fluid-structure interaction (FSI) problems involving inviscid compressible fluids interacting with nonlinear solids that undergo large rotations and displacements. The computational approach is a mixed Eulerian-Lagrangian scheme that makes use of deforming composite grids (DCG) to treat large changes in the geometry in an accurate, flexible, and robust manner. The current work extends the AMP algorithm developed in Banks et al. [1] for linearly elasticity to the case of nonlinear solids. To ensure stability for the case of light solids, the new AMP algorithm embeds an approximate solution of a nonlinear fluid-solid Riemann (FSR) problem into the interface treatment. The solution to the FSR problem is derived and shown to be of a similar form to that derived for linear solids: the state on the interface being fundamentally an impedance-weighted average of the fluid and solid states. Numerical simulations demonstrate that the AMP algorithm is stable even for light solids when added-mass effects are large. The accuracy and stability of the AMP scheme is verified by comparison to an exact solution using the method of analytical solutions and to a semi-analytical solution that is obtained for a rotating solid disk immersed in a fluid. The scheme is applied to the simulation of a planar shock impacting a light elliptical-shaped solid, and comparisons are made between solutions of the FSI problem for a neo-Hookean solid, a linearly elastic solid, and a rigid solid. The ability of the approach to handle large deformations is demonstrated for a problem of a high-speed flow past a light, thin, and flexible solid beam.
Santee, G.E. Jr.; Chang, F.H.; Mortensen, G.A.; Brockett, G.F.; Gross, M.B.; Belytschko, T.B.
1982-11-01
This report, the third in a series of reports for RP-1065, describes the final step in the stepwise approach for developing the three-dimensional, nonlinear, fluid-structure interaction methodology to assess the hydroloads on a large PWR during the subcooled portions of a hypothetical LOCA. The final step in the methodology implements enhancements and special modifications to the STEALTH 3D computer program and the WHAMSE 3D computer program. After describing the enhancements, the individual and the coupled computer programs are assessed by comparing calculational results with either analytical solutions or with experimental data. The coupled 3D STEALTH/WHAMSE computer program is then applied to the simulation of HDR Test V31.1 to further assess the program and to investigate the role that fluid-structure interaction plays in the hydrodynamic loading of reactor internals during subcooled blowdown.
Moses, Edward I.
1992-01-01
A laser pulse stacking method is disclosed. A problem with the prior art has been the generation of a series of laser beam pulses where the outer and inner regions of the beams are generated so as to form radially non-synchronous pulses. Such pulses thus have a non-uniform cross-sectional area with respect to the outer and inner edges of the pulses. The present invention provides a solution by combining the temporally non-uniform pulses in a stacking effect to thus provide a more uniform temporal synchronism over the beam diameter.
Moses, E.I.
1992-12-01
A laser pulse stacking method is disclosed. A problem with the prior art has been the generation of a series of laser beam pulses where the outer and inner regions of the beams are generated so as to form radially non-synchronous pulses. Such pulses thus have a non-uniform cross-sectional area with respect to the outer and inner edges of the pulses. The present invention provides a solution by combining the temporally non-uniform pulses in a stacking effect to thus provide a more uniform temporal synchronism over the beam diameter. 2 figs.
The effect of Coulomb interactions on nonlinear thermovoltage and thermocurrent in quantum dots
NASA Astrophysics Data System (ADS)
Zimbovskaya, Natalya A.
2015-06-01
In the present work, we theoretically study the nonlinear regime of charge transport through a quantum dot coupled to the source and drain reservoirs. The investigation is carried out using a nonequilibrium Green's function formalism beyond the Hartree-Fock approximation. Employed approximations for the relevant Green's functions allow to trace a transition from Coulomb blockade regime to Kondo regime in the thermoelectric transport. Effects arising when electrons move in response to thermal gradient applied across the system are discussed, including experimentally observed thermovoltage zeros.
Nonlinear Interaction of Intense Attosecond XUV Pulses with Atoms and Molecules
NASA Astrophysics Data System (ADS)
Midorikawa, K.; Shimizu, T.; Nabekawa, Y.
We have observed nonlinear optical processes such as two-photon double ionization and above threshold ionization of rare gases in the xuv region with intense high-order harmonics. Using two-photon double ionization in He, the pulse width of the 27th (42 eV) harmonic was measured by an autocorrelation technique, and found it to be 8 ns. A train of attosecond pulses was also characterized directly by the energy-resolved autocorrelation of the above threshold ionized electrons.
Kribs-Zaleta, Christopher M
2013-01-01
Mathematical models are well-established as metaphors for biological and epidemiological systems. The framework of epidemic modeling has also been applied to sociological phenomena driven by peer pressure, notably in two dozen dynamical systems research projects developed through the Mathematical and Theoretical Biology Institute, and popularized by authors such as Gladwell (2000). This article reviews these studies and their common structures, and identifies a new mathematical metaphor which uses multiple nonlinearities to describe the multiple thresholds governing the persistence of hierarchical phenomena, including the situation termed a "backward bifurcation'' in mathematical epidemiology, where established phenomena can persist in circumstances under which the phenomena could not initially emerge. PMID:24245636
Nonlinear vortex-phonon interactions in a Bose–Einstein condensate
NASA Astrophysics Data System (ADS)
Mendonça, J. T.; Haas, F.; Gammal, A.
2016-07-01
We consider the nonlinear coupling between an exact vortex solution in a Bose–Einstein condensate and a spectrum of elementary excitations in the medium. These excitations, or Bogoliubov–de Gennes modes, are indeed a special kind of phonons. We treat the spectrum of elementary excitations in the medium as a gas of quantum particles, sometimes also called bogolons. An exact kinetic equation for the bogolon gas is derived, and an approximate form of this equation, valid in the quasi-classical limit, is also obtained. We study the energy transfer between the vortex and the bogolon gas, and establish conditions for vortex instability and damping.
Nonlinear interaction of intense hypergeometric Gaussian subfamily laser beams in plasma
NASA Astrophysics Data System (ADS)
Sobhani, H.; Vaziri (Khamedi), M.; Rooholamininejad, H.; Bahrampour, A. R.
2016-07-01
Propagation of Hypergeometric-Gaussian laser beam in a nonlinear plasma medium is investigated by considering the Source Dependent Expansion method. A subfamily of Hypergeometric-Gaussian beams with a non-negative, even and integer radial index, can be expressed as the linear superposition of finite number of Laguerre-Gaussian functions. Propagation of Hypergeometric-Gaussian beams in a nonlinear plasma medium depends on the value of radial index. The bright rings' number of these beams is changed during the propagation in plasma medium. The effect of beam vortex charge number l and initial (input) beam intensity on the self-focusing of Hypergeometric-Gaussian beams is explored. Also, by choosing the suitable initial conditions, Hypergeometric-Gaussian subfamily beams can be converted to one or more mode components that a typical of mode conversion may be occurred. The self-focusing of these winding beams can be used to control the focusing force and improve the electron bunch quality in laser plasma accelerators.
Technology Transfer Automated Retrieval System (TEKTRAN)
Efficient methods of stacking genes into plant genomes are needed to expedite transfer of multigenic traits into diverse crops grown in a variety of environments. Over two decades of research has identified several site-specific recombinases that carry out efficient cis and trans recombination betw...
The report gives results of technical and economic evaluations of stack gas reheat (SGR) following wet flue gas desulfurization (FGD) for coal-fired power plants. The evaluations were based on information from literature and a survey of FGD users, vendors, and architect/engineer ...
NASA Astrophysics Data System (ADS)
Hall, P.; Smith, F. T.
1988-06-01
The development of Tollmien-Schlichting waves (TSWs) and Taylor-Goertler vortices (TGVs) in fully developed viscous curved-channel flows is investigated analytically, with a focus on their nonlinear interactions. Two types of interactions are identified, depending on the amplitude of the initial disturbances. In the low-amplitude type, two TSWs and one TGV interact, and the scaled amplitudes go to infinity on a finite time scale; in the higher-amplitude type, which can also occur in a straight channel, the same singularity occurs if the angle between the TSW wavefront and the TGV is greater than 41.6 deg, but the breakdown is exponential and takes an infinite time if the angle is smaller. The implications of these findings for external flow problems such as the design of laminar-flow wings are indicated. It is concluded that longitudinal vortices like those observed in the initial stages of the transition to turbulence can be produced unless the present interaction mechanism is destroyed by boundary-layer growth.
NASA Technical Reports Server (NTRS)
Hall, P.; Smith, F. T.
1988-01-01
The development of Tollmien-Schlichting waves (TSWs) and Taylor-Goertler vortices (TGVs) in fully developed viscous curved-channel flows is investigated analytically, with a focus on their nonlinear interactions. Two types of interactions are identified, depending on the amplitude of the initial disturbances. In the low-amplitude type, two TSWs and one TGV interact, and the scaled amplitudes go to infinity on a finite time scale; in the higher-amplitude type, which can also occur in a straight channel, the same singularity occurs if the angle between the TSW wavefront and the TGV is greater than 41.6 deg, but the breakdown is exponential and takes an infinite time if the angle is smaller. The implications of these findings for external flow problems such as the design of laminar-flow wings are indicated. It is concluded that longitudinal vortices like those observed in the initial stages of the transition to turbulence can be produced unless the present interaction mechanism is destroyed by boundary-layer growth.
23. Brick coke quencher, brick stack, metal stack to right, ...
23. Brick coke quencher, brick stack, metal stack to right, coke gas pipe to left; in background, BOF building, limestone piles, Levy's Slag Dump. Looking north/northwest - Rouge Steel Company, 3001 Miller Road, Dearborn, MI
Zimbovskaya, Natalya A
2016-07-27
In this paper, we theoretically analyze steady-state thermoelectric transport through a single-molecule junction with a vibrating bridge. The thermally induced charge current in the system is explored using a nonequilibrium Green function formalism. We study the combined effects of Coulomb interactions between charge carriers on the bridge and electron-phonon interactions on the thermocurrent beyond the linear response regime. It is shown that electron-vibron interactions may significantly affect both the magnitude and the direction of the thermocurrent, and vibrational signatures may appear. PMID:27248442
NASA Astrophysics Data System (ADS)
Zimbovskaya, Natalya A.
2016-07-01
In this paper, we theoretically analyze steady-state thermoelectric transport through a single-molecule junction with a vibrating bridge. The thermally induced charge current in the system is explored using a nonequilibrium Green function formalism. We study the combined effects of Coulomb interactions between charge carriers on the bridge and electron–phonon interactions on the thermocurrent beyond the linear response regime. It is shown that electron–vibron interactions may significantly affect both the magnitude and the direction of the thermocurrent, and vibrational signatures may appear.
NASA Technical Reports Server (NTRS)
Tkalcevic, S.
1982-01-01
The longitudinal resonance of waves and energetic electrons in the Earth's magnetosphere, and the possible role this resonance may play in generating various magnetospheric phenomena are studied. The derivation of time-averaged nonlinear equations of motion for energetic particles longitudinally resonant with a whistler mode wave propagating with nonzero wave normal is considered. It is shown that the wave magnetic forces can be neglected at lower particle pitch angles, while they become equal to or larger than the wave electric forces for alpha 20 deg. The time-averaged equations of motion were used in test particle simulation which were done for a wide range of wave amplitudes, wave normals, particle pitch angles, particle parallel velocities, and in an inhomogeneous medium such as the magnetosphere. It was found that there are two classes of particles, trapped and untrapped, and that the scattering and energy exchange for those two groups exhibit significantly different behavior.
Helical waves and non-linear dynamics of fluid/structure interactions in a tube row
Moon, F.C.; Thothadri, M.
1997-12-31
The goal of this study has been to investigate low-dimensional models for fluid-structure dynamics of flow across a row of cylindrical tubes. Four principle results of this experimental-theoretical study are discussed. (i) Experimental evidence has shown that the dynamic instability of the tube row is a subcritical Hopf bifurcation. (ii) The critical flow velocity decreases as the number of flexible cylinders increases. (iii) The linear model exhibits coupled helical wave solutions in the tube dynamics. (iv) A nonlinear model of the tube motions shows a complex subcritical Hopf bifurcation with a secondary bifurcation to a torus or quasi-periodic oscillation. In this analysis the tools of center manifolds, normal forms and numerical simulation are used.
Khorashadizadeh, S. M.; Rastbood, E.; Zeinaddini Meymand, H.; Niknam, A. R.
2013-08-15
The nonlinear coupling between circularly polarized electromagnetic (CPEM) waves and acoustic-like waves in a magnetoactive electron-positron-ion (e-p-i) plasma is studied, taking into account the relativistic motion of electrons and positrons. The possibility of modulational instability and its growth rate as well as the envelope soliton formation and its characteristics in such plasmas are investigated. It is found that the growth rate of modulation instability increases in the case that ω{sub c}/ω<1 (ω{sub c} and ω are the electron gyrofrequency and the CPEM wave frequency, respectively) and decreases in the case that ω{sub c}/ω>1. It is also shown that in a magnetoactive e-p-i plasma, the width of bright soliton increases/decreases in case of (ω{sub c}/ω)<1/(ω{sub c}/ω)>1 by increasing the magnetic field strength.
Interactions of nonlinear electron-acoustic solitary waves with vortex electron distribution
Demiray, Hilmi
2015-02-15
In the present work, based on a one dimensional model, we consider the head-on-collision of nonlinear electron-acoustic waves in a plasma composed of a cold electron fluid, hot electrons obeying a trapped/vortex-like distribution, and stationary ions. The analysis is based on the use of extended Poincare, Lighthill-Kuo method [C. H. Su and R. M. Mirie, J. Fluid Mech. 98, 509 (1980); R. M. Mirie and C. H. Su, J. Fluid Mech. 115, 475 (1982)]. It is shown that, for the first order approximation, the waves propagating in opposite directions are characterized by modified Korteweg-de Vries equations. In contrary to the results of previous investigations on this subject, we showed that the phase shifts are functions of both amplitudes of the colliding waves. The numerical results indicate that the waves with larger amplitude experience smaller phase shifts. Such a result seems to be plausible from physical considerations.
NASA Astrophysics Data System (ADS)
Krasnoselskikh, V.; Artemyev, A.; Agapitov, O. V.; Mourenas, D.
2013-12-01
We present selected THEMIS observations of highly-oblique and large amplitude chorus waves at medium latitudes. The major part of observed waves propagates at nearly-electrostatic mode with normal angles close to resonance cone. We use test particle simulations and analytical theory to estimate efficiency of nonlinear particle acceleration by these waves via Landau and fundamental cyclotron resonances. We show that trapping into the Landau resonance corresponds to a decrease of electron equatorial pitch-angles, while trapping into the first cyclotron resonance increases electron equatorial pitch-angles. For 100 keV electrons, the energy gain is larger for the trapping due to Landau resonance. Moreover, trapping into the Landau resonance is accessible for a wider range of initial pitch-angles in comparison with the fundamental resonance.
NASA Astrophysics Data System (ADS)
Chakraborty, Suman; Chatterjee, Dipankar; Bakli, Chirodeep
2013-05-01
We discover a nonlinear coupling between the hydrophobicity of a charged substrate and electrokinetic pumping in narrow fluidic confinements. Our analyses demonstrate that the effective electrokinetic transport in nanochannels may get massively amplified over a regime of bare surface potentials and may subsequently get attenuated beyond a threshold surface charging condition because of a complex interplay between reduced hydrodynamic resistance on account of the spontaneous inception of a less dense interfacial phase and ionic transport within the electrical double layer. We also show that the essential physics delineated by our mesoscopic model, when expressed in terms of a simple mathematical formula, agrees remarkably with that portrayed by molecular dynamics simulations. The nontrivial characteristics of the initial increment followed by a decrement of the effective zeta potential with a bare surface potential may open up the realm of hitherto-unexplored operating regimes of electrohydrodynamically actuated nanofluidic devices.
Sharma, R. P.; Gupta, M. K.
2006-11-15
In this paper, the authors have investigated the effect of ultra-intense laser beam filaments on stimulated Raman scattering (SRS) in unmagnetized plasma when relativistic and ponderomotive nonlinearities are operative. First, the filamentary dynamics of laser beam is studied. In these structures, the plasma wave generation and associated SRS process are studied. The effect of filamentation on SRS back reflectivity has been studied in detail. For the typical laser plasma parameters, i.e., laser beam Nd:YAG ({lambda}=1064 nm), laser beam radius=15 {mu}m, laser power flux=6x10{sup 17} W/cm{sup 2}, electron density=1.9x10{sup 19} per cm{sup 3}, the SRS reflectivity reduces by a factor 2.5 due to ponderomotive effects.
Generation of 1.5-octave intense infrared pulses by nonlinear interactions in DAST crystal
NASA Astrophysics Data System (ADS)
Vicario, C.; Monoszlai, B.; Arisholm, G.; Hauri, C. P.
2015-09-01
Infrared pulses with large spectral width extending from 1.2 to 3.4 μm are generated in the organic crystal DAST (4-N, N-dimethylamino-4‧-N‧-methylstilbazolium tosylate). The input pulse has a central wavelength of 1.5 μm and 65 fs duration. With 2.8 mJ input energy we obtained up to 700 μJ in the broadened spectrum. The output can be easily scaled up in energy by increasing the crystal size together with the energy and the beam size of the pump. The ultra-broad spectrum is ascribed to cascaded second order processes mediated by the exceptionally large effective χ 2 nonlinearity of DAST, but the shape of the spectrum indicates that a delayed χ 3 process may also be involved. Numerical simulations reproduce the experimental results qualitatively and provide an insight in the mechanisms underlying the asymmetric spectral broadening.
Fu, Heidi Li-Ki; Po, Charlotte; He, Hexiang; Leung, Sammual Yu-Lut; Wong, Kam Sing; Yam, Vivian Wing-Wah
2016-08-01
A series of newly synthesized dicyanoplatinum(II) 2,2'-bipyridine complexes exhibits self-assembly properties in solution after the incorporation of the l-valine amino units appended with various hydrophobic motifs. These l-valine-derived substituents were found to have critical control over the aggregation behaviors of the complexes in the solution state. On one hand, one of the complexes was found to exhibit interesting circularly polarized luminescence (CPL) signals at low temperature due to the formation of chiral spherical aggregates in the temperature-dependent studies. On the other hand, systematic transformation from less uniform aggregates to well-defined fibrous and rod-like structures via Pt⋅⋅⋅Pt and π-π stacking interactions has also been observed in the mixed-solvent studies. These changes were monitored by UV/Vis absorption, emission, circular dichroism (CD), and CPL spectroscopies, and morphologies were studied by electron microscopy. PMID:27412571
NASA Astrophysics Data System (ADS)
Kornienko, L. S.; Kravtsov, N. V.; Shelaev, A. N.
1985-01-01
It is found experimentally that the competitive interaction of the oppositely directed (OD) light waves in YAG:Nd3+ and ruby solid-state ring lasers OIRL) can be significantly reduced due to nonlinear optical effects (second harmonic generation, stimulated Raman scattering, resonant absorption) since the nonlinear losses for the wave of lower intensity are lower. It was established that in the SRL with a resonantly absorbing medium the spatially inhomogeneous burning-out and the slowness of the relaxation of the inverted population in the solid-state active medium may result in strong phase nonreciprocity due to the frequency shift of the OD waves after their reflection from the moving lattice of the inverted population. The beat frequency strongly depends on detuning between the gain and absorption lines and may be more than two orders of magnitude less in comparison with the resonator frequency difference in the rotating SRL. The possibility has been shown of active stabilization of the bidirectional generation in the beat regime using the nonreciprocal amplitude Faraday element controlled by the external feedback circuit via the difference of the OD waves intensities.
NASA Astrophysics Data System (ADS)
Tang, Bing; Li, De-Jun
2016-05-01
A theoretical work on quantum breathers in a nonlinear Klein-Gordon lattice model with nearest and next-nearest neighbor interactions is presented. The semiclassical and the full quantum cases are respectively considered. For the semiclassical case, we obtain the analytical solution of discrete breather, and find that the wave number corresponding to the appearance of discrete breather changes when the ratio of the next-nearest- to -nearest - neighbor harmonic force constants is greater than 1/4. For the full quantum case, by calculating the energy spectrum of the system containing two quanta, we prove numerically the existence of quantum breathers (two-quanta bound states) and find the shape of energy spectrum changes dramatically as the value of next -nearest neighbor harmonic force constant increasing.
NASA Astrophysics Data System (ADS)
Zhang, Y. L.; Matsumoto, H.; Omura, Y.
1993-12-01
Both linear and nonlinear interactions between oblique whistler, electrostatic, quasi-upper hybrid mode waves and an electron beam are studied by linear analyses and electromagnetic particle simulations. In addition to a background cold plasma, we assumed a hot electron beam drifting along a static magnetic field. Growth rates of the oblique whistler, oblique electrostatic, and quasi-upper hybrid instabilities were first calculated. We found that there are four kinds of unstable mode waves for parallel and oblique propagations. They are the electromagnetic whistler mode wave (WW1), the electrostatic whistler mode wave (WW2), the electrostatic mode wave (ESW), and the quasi-upper hybrid mode wave (UHW). A possible mechanism is proposed to explain the satellite observations of whistler mode chorus and accompanied electrostatic waves, whose amplitudes are sometimes modulated at the chorus frequency.
Castro, G; Mascali, D; Agnello, R; Celona, L; Leonardi, O; Neri, L; Nicolosi, D; Torrisi, G; Gammino, S
2016-02-01
A characterization of wave-to-plasma interaction in a quasi-flat magnetostatic field at 3.75 GHz has been carried out by using a small-wire movable RF antenna, connected to a spectrum analyzer. The coupling between electromagnetic and electrostatic waves leads to a characteristic spectral emission in low frequency range and around the pumping wave frequency. The most relevant results consist in the broadening of the pumping wave spectrum above critical RF power thresholds and in the generation of sidebands of the pumping frequency, with corresponding components in low frequency domain. The non-linearities are accompanied by the generation of overdense plasmas and intense fluxes of X-rays. PMID:26931915
LETTER On the nonlinear response of a particle interacting with fermions in a 1D lattice
NASA Astrophysics Data System (ADS)
Zotos, X.
2010-12-01
By the Bethe ansatz method we study the energy dispersion of a particle interacting by a local interaction with fermions (or hard core bosons) of equal mass in a one-dimensional lattice. We focus on the period of the Bloch oscillations, which turns out to be related to the Fermi wavevector of the Fermi sea and in particular on how this dispersion emerges as a collective effect in the thermodynamic limit. We also discuss the adiabatic coherent collective response of the system to an applied field.
NASA Technical Reports Server (NTRS)
Gupta, R. N.; Rodkiewicz, C. M.
1975-01-01
The numerical results are obtained for heat transfer, skin-friction, and viscous interaction induced pressure for a step-wise accelerated flat plate in hypersonic flow. In the unified approach here the results are presented for both weak and strong-interaction problems without employing any linearization scheme. With the help of the numerical method used in this work an accurate prediction of wall shear can be made for the problems with plate velocity changes of 1% or larger. The obtained results indicate that the transient contribution to the induced pressure for helium is greater than that for air.
NASA Astrophysics Data System (ADS)
Hu, Kun; Peng, C. K.; Huang, Norden E.; Wu, Zhaohua; Lipsitz, Lewis A.; Cavallerano, Jerry; Novak, Vera
2008-04-01
Cerebral autoregulation is an important mechanism that involves dilatation and constriction in arterioles to maintain relatively stable cerebral blood flow in response to changes of systemic blood pressure. Traditional assessments of autoregulation focus on the changes of cerebral blood flow velocity in response to large blood pressure fluctuations induced by interventions. This approach is not feasible for patients with impaired autoregulation or cardiovascular regulation. Here we propose a newly developed technique-the multimodal pressure-flow (MMPF) analysis, which assesses autoregulation by quantifying nonlinear phase interactions between spontaneous oscillations in blood pressure and flow velocity during resting conditions. We show that cerebral autoregulation in healthy subjects can be characterized by specific phase shifts between spontaneous blood pressure and flow velocity oscillations, and the phase shifts are significantly reduced in diabetic subjects. Smaller phase shifts between oscillations in the two variables indicate more passive dependence of blood flow velocity on blood pressure, thus suggesting impaired cerebral autoregulation. Moreover, the reduction of the phase shifts in diabetes is observed not only in previously-recognized effective region of cerebral autoregulation (<0.1 Hz), but also over the higher frequency range from ˜0.1 to 0.4 Hz. These findings indicate that type 2 diabetes mellitus alters cerebral blood flow regulation over a wide frequency range and that this alteration can be reliably assessed from spontaneous oscillations in blood pressure and blood flow velocity during resting conditions. We also show that the MMPF method has better performance than traditional approaches based on Fourier transform, and is more suitable for the quantification of nonlinear phase interactions between nonstationary biological signals such as blood pressure and blood flow.
Energy Expenditure of Sport Stacking
ERIC Educational Resources Information Center
Murray, Steven R.; Udermann, Brian E.; Reineke, David M.; Battista, Rebecca A.
2009-01-01
Sport stacking is an activity taught in many physical education programs. The activity, although very popular, has been studied minimally, and the energy expenditure for sport stacking is unknown. Therefore, the purposes of this study were to determine the energy expenditure of sport stacking in elementary school children and to compare that value…
Iridium Interfacial Stack (IRIS)
NASA Technical Reports Server (NTRS)
Spry, David James (Inventor)
2015-01-01
An iridium interfacial stack ("IrIS") and a method for producing the same are provided. The IrIS may include ordered layers of TaSi.sub.2, platinum, iridium, and platinum, and may be placed on top of a titanium layer and a silicon carbide layer. The IrIS may prevent, reduce, or mitigate against diffusion of elements such as oxygen, platinum, and gold through at least some of its layers.
MPI parallelization of Vlasov codes for the simulation of nonlinear laser-plasma interactions
NASA Astrophysics Data System (ADS)
Savchenko, V.; Won, K.; Afeyan, B.; Decyk, V.; Albrecht-Marc, M.; Ghizzo, A.; Bertrand, P.
2003-10-01
The simulation of optical mixing driven KEEN waves [1] and electron plasma waves [1] in laser-produced plasmas require nonlinear kinetic models and massive parallelization. We use Massage Passing Interface (MPI) libraries and Appleseed [2] to solve the Vlasov Poisson system of equations on an 8 node dual processor MAC G4 cluster. We use the semi-Lagrangian time splitting method [3]. It requires only row-column exchanges in the global data redistribution, minimizing the total number of communications between processors. Recurrent communication patterns for 2D FFTs involves global transposition. In the Vlasov-Maxwell case, we use splitting into two 1D spatial advections and a 2D momentum advection [4]. Discretized momentum advection equations have a double loop structure with the outer index being assigned to different processors. We adhere to a code structure with separate routines for calculations and data management for parallel computations. [1] B. Afeyan et al., IFSA 2003 Conference Proceedings, Monterey, CA [2] V. K. Decyk, Computers in Physics, 7, 418 (1993) [3] Sonnendrucker et al., JCP 149, 201 (1998) [4] Begue et al., JCP 151, 458 (1999)
The effects of nonlinear interactions and network structure in small group opinion dynamics
NASA Astrophysics Data System (ADS)
Gabbay, Michael
2007-05-01
We present a model of opinion dynamics in social networks in which an individual's opinion evolves under the action of (i) a linear force which tends to restore the opinion back towards the individual's natural bias that is his or her initial opinion and (ii) a nonlinear coupling with other individuals which acts to bring opinions closer together but wanes for high opinion discrepancies. Bifurcation analysis for the case of a two-person group shows that a critical value for the difference in natural biases exists which demarcates regimes of qualitatively different behavior. For low to moderate natural bias differences, the dynamics are qualitatively similar to linear theory. For high bias differences, the system takes on a binary nature and is marked by discontinuous transitions between deadlock and consensus as well as hysteresis as the coupling is varied. The coupling required to force consensus grows extremely rapidly with the natural bias difference indicating that trying to achieve group consensus solely via increasing the communications rate becomes fruitless as the biases become extremely divergent. We also show that, for high bias differences, a triad broker network topology can reduce group discord more effectively than a clique, contrary to linear theory.
Thermoacoustic Refrigerator's Stack Optimization
NASA Astrophysics Data System (ADS)
El-Fawal, Mawahib Hassan; Mohd-Ghazali, Normah; Yaacob, Mohd. Shafik; Darus, Amer Nordin
2010-06-01
The standing wave thermoacoustic refrigerator, which uses sound generation to transfer heat, was developed rapidly during the past four decades. It was regarded as a new, promising and environmentally benign alternative to conventional compression vapor refrigerators, although it was not competitive regarding the coefficient of performance (COP) yet. Thus the aim of this paper is to enhance thermoacoustic refrigerator's stack performance through optimization. A computational optimization procedure of thermoacoustic stack design was fully developed. The procedure was designed to achieve optimal coefficient of performance based on most of the design and operating parameters. Cooling load and acoustic power governing equations were set assuming the linear thermoacoustic theory. Lagrange multipliers method was used as an optimization technique tool to solve the governing equations. Numerical analyses results of the developed design procedure are presented. The results showed that the stack design parameters are the most significant parameters for the optimal overall performance. The coefficient of performance obtained increases by about 48.8% from the published experimental optimization methods. The results are in good agreement with past established studies.
Harbola, Upendra; Mukamel, Shaul
2004-11-01
Electrostatic and dispersive interactions of polarizable molecules are expressed in terms of generalized (nonretarded) charge-density response functions of the isolated molecules, which in turn are expanded using the collective electronic oscillator (CEO) eigenmodes of linearized time-dependent density-functional theory. Closed expressions for the intermolecular energy are derived to sixth order in charge fluctuation amplitudes.
ERIC Educational Resources Information Center
Palilonis, Jennifer; Butler, Darrell; Leidig-Farmen, Pamela
2013-01-01
As online teaching techniques continue to evolve, new opportunities surface for research and insight regarding best practices for the development and implementation of interactive, multimedia teaching and learning tools. These tools are particularly attractive for courses that lend themselves to a rich media approach. Such is the case for visual…
Nonlinear adhesion dynamics of confined lipid membranes
NASA Astrophysics Data System (ADS)
To, Tung; Le Goff, Thomas; Pierre-Louis, Olivier
Lipid membranes, which are ubiquitous objects in biological environments are often confined. For example, they can be sandwiched between a substrate and the cytoskeleton between cell adhesion, or between other membranes in stacks, or in the Golgi apparatus. We present a study of the nonlinear dynamics of membranes in a model system, where the membrane is confined between two flat walls. The dynamics derived from the lubrication approximation is highly nonlinear and nonlocal. The solution of this model in one dimension exhibits frozen states due to oscillatory interactions between membranes caused by the bending rigidity. We develope a kink model for these phenomena based on the historical work of Kawasaki and Otha. In two dimensions, the dynamics is more complex, and depends strongly on the amount of excess area in the system. We discuss the relevance of our findings for experiments on model membranes, and for biological systems. Supported by the grand ANR Biolub.
Memory Stacking in Hierarchical Networks.
Westö, Johan; May, Patrick J C; Tiitinen, Hannu
2016-02-01
Robust representations of sounds with a complex spectrotemporal structure are thought to emerge in hierarchically organized auditory cortex, but the computational advantage of this hierarchy remains unknown. Here, we used computational models to study how such hierarchical structures affect temporal binding in neural networks. We equipped individual units in different types of feedforward networks with local memory mechanisms storing recent inputs and observed how this affected the ability of the networks to process stimuli context dependently. Our findings illustrate that these local memories stack up in hierarchical structures and hence allow network units to exhibit selectivity to spectral sequences longer than the time spans of the local memories. We also illustrate that short-term synaptic plasticity is a potential local memory mechanism within the auditory cortex, and we show that it can bring robustness to context dependence against variation in the temporal rate of stimuli, while introducing nonlinearities to response profiles that are not well captured by standard linear spectrotemporal receptive field models. The results therefore indicate that short-term synaptic plasticity might provide hierarchically structured auditory cortex with computational capabilities important for robust representations of spectrotemporal patterns. PMID:26654206
NONLINEAR WAVE INTERACTIONS AS EMISSION PROCESS OF TYPE II RADIO BURSTS
Ganse, Urs; Kilian, Patrick; Spanier, Felix; Vainio, Rami
2012-06-01
The emission of fundamental and harmonic frequency radio waves of type II radio bursts are assumed to be products of three-wave interaction processes of beam-excited Langmuir waves. Using a particle-in-cell code, we have performed simulations of the assumed emission region, a coronal mass ejection foreshock with two counterstreaming electron beams. Analysis of wavemodes within the simulation shows self-consistent excitation of beam-driven modes, which yield interaction products at both fundamental and harmonic emission frequencies. Through variation of the beam strength, we have investigated the dependence of energy transfer into electrostatic and electromagnetic modes, confirming the quadratic dependence of electromagnetic emission on electron beam strength.
Frequency response areas in the inferior colliculus: nonlinearity and binaural interaction
Yu, Jane J.; Young, Eric D.
2013-01-01
The tuning, binaural properties, and encoding characteristics of neurons in the central nucleus of the inferior colliculus (CNIC) were investigated to shed light on nonlinearities in the responses of these neurons. Results were analyzed for three types of neurons (I, O, and V) in the CNIC of decerebrate cats. Rate responses to binaural stimuli were characterized using a 1st- plus 2nd-order spectral integration model. Parameters of the model were derived using broadband stimuli with random spectral shapes (RSS). This method revealed four characteristics of CNIC neurons: (1) Tuning curves derived from broadband stimuli have fixed (i. e., level tolerant) bandwidths across a 50–60 dB range of sound levels; (2) 1st-order contralateral weights (particularly for type I and O neurons) were usually larger in magnitude than corresponding ipsilateral weights; (3) contralateral weights were more important than ipsilateral weights when using the model to predict responses to untrained noise stimuli; and (4) 2nd-order weight functions demonstrate frequency selectivity different from that of 1st-order weight functions. Furthermore, while the inclusion of 2nd-order terms in the model usually improved response predictions related to untrained RSS stimuli, they had limited impact on predictions related to other forms of filtered broadband noise [e. g., virtual-space stimuli (VS)]. The accuracy of the predictions varied considerably by response type. Predictions were most accurate for I neurons, and less accurate for O and V neurons, except at the lowest stimulus levels. These differences in prediction performance support the idea that type I, O, and V neurons encode different aspects of the stimulus: while type I neurons are most capable of producing linear representations of spectral shape, type O and V neurons may encode spectral features or temporal stimulus properties in a manner not easily explained with the low-order model. Supported by NIH grant DC00115. PMID:23675323
Cerezo, M Angeles; Pons-Salvador, Gemma; Trenado, Rosa M; Sierra, Purificacion
2016-10-01
This longitudinal study examined flexibility in early mother-infant interaction at the age of approximately 6 months (N=30) and whether flexibility indices predicted (in) secure child attachment at 15 months. Dyadic flexibility was measured using dynamic systems-based modelling of patterns during mother-child free play in terms of NDS variables derived from SSG: the propensity to change states (dynamic flexibility), number of states visited (diversity) and predictability (dispersion). Results showed significant discriminant functions on the attachment type groups, A, B & C, for the total grid, which included verbal and non-verbal, and for the reciprocal verbal region. Specifically, the prediction outcomes seem to work better in total grid for A-dyads and in the reciprocal verbal region for B and C-dyads. Diversity emerged as the most relevant index in dyadic flexibility: A-dyads showed the least diversity, distinguished them from B-dyads in the verbal regions, (both the reciprocal and non-reciprocal, 'child verbal-mother non-verbal' one), and, from C-dyads in the reciprocal non-verbal region. A-dyads showed remarkably low activity in the regions involving child verbal behavior, showing that children who became avoidant attached at 15 months of age, were mostly silent at approximately 6 months, when they interacted with their mothers. Findings in this study contribute to advancing conceptually informed measurement of dyadic interaction to provide a new perspective on maternal sensitivity and early markers of child insecure/secure attachment. PMID:27550705
Bezhanov, S G; Uryupin, S A
2013-11-30
Nonlinear currents slowly varying in time are found in the skin layer of a metal irradiated by short laser pulses. The low-frequency field generated by the nonlinear currents in metal and vacuum is studied. The spectral composition, energy and shape of the low-frequency radiation pulse are described. (nonlinear optical phenomena)
Stacking attributes from local slopes
NASA Astrophysics Data System (ADS)
Ghosh, S.; Gajewski, D.; Dell, S.; Nath, S. K.; Wave Inversion Technology (Wit) Consortium
2010-12-01
CMP stacking is controlled by the stacking velocity which is determined by a one-dimendional optimization procedure using semblance as a coherence criterion. New multi-parameter stacking formulas like the Common Reflection Surface (CRS) operator consider neighboring CMP locations in the stack. These methods stack considerably more traces than conventional CMP processing leading to stacked sections with an improved signal-to-nose ratio and better image quality. The corresponding stacking trajectories are controlled by three stacking attributes for the 2-D case and eight for the 3-D case. The determination of these attributes requires a multi-dimensional optimization procedure which is time consuming. If we know good starting values, we can limit the search intervals considerably and speed up the process. It was shown that the stacking attributes are linked to local slopes in seismic zero offset and constant offset sections. Therefore, the determination of local slopes can guide the choice of the search intervals in the optimization procedure. We use structural tensors for the determination of local slopes. Structural tensors represent a versatile tool to investigate coherent features in the data superior to other slop determination tools like slant stacking or plane wave destructors. The window size is adjustable and allows to optimize smoothing and smearing in the slope determination process where the smoothing can be performed along structural events (directional smoothing). This smart feature helps to consider complex geologies and acknowledges faults and conflicting dips without any significant change in computation time. Different variants of the algorithm are used to determine slopes in CMP gathers, stacked and time or depth migrated sections. The results of the local slope determinations are used to compute stacking attributes for the CRS method. We compare these to stacking attributes obtained from optimization. The attributes determined from local slopes
NASA Astrophysics Data System (ADS)
Dey, Prasenjit
understanding the basic unexplored science as well as creating technological developments. The dephasing dynamics in semiconductors typically occur in the picosecond to femtosecond timescale, thus the use of ultrafast laser spectroscopy is a potential route to probe such excitonic responses. The focus of this dissertation is two-fold: firstly, to develop the necessary instrumentation to accurately probe the aforementioned parameters and secondly, to explore the quantum dynamics and the underlying many-body interactions in different layered semiconducting materials. A custom-built multidimensional optical non-linear spectrometer was developed in order to perform two-dimensional spectroscopic (2DFT) measurements. The advantages of this technique are multifaceted compared to regular one-dimensional and non-linear incoherent techniques. 2DFT technique is based on an enhanced version of Four wave mixing experiments. This powerful tool is capable of identifying the resonant coupling, probing the coherent pathways, unambiguously extracting the homogeneous linewidth in the presence of inhomogeneity and decomposing a complex spectra into real and imaginary parts. It is not possible to uncover such crucial features by employing one dimensional non-linear technique. Monolayers as well as bulk TMDs and group III-VI bulk layered materials are explored in this dissertation. The exciton quantum dynamics is explored with three pulse four-wave mixing whereas the phase sensitive measurements are obtained by employing two-dimensional Fourier transform spectroscopy. Temperature and excitation density dependent 2DFT experiments unfold the information associated with the many-body interactions in the layered semiconducting samples.
Nonlinear theory of beam-wave interaction in the pasotron with a phase-mixed electron beam
Bliokh, Yu.P.; Nusinovich, G.S.
2006-02-15
The nonlinear theory describing the interaction processes in traveling-wave-amplifier (TWT) and backward-wave-oscillator (BWO) configurations of pasotrons is developed. It is shown that space charge forces in electron bunches formed in the process of beam-wave interaction in the pasotron play a role completely different from that in linear-beam devices with a strong magnetic focusing of electron beams. While in the latter devices the space charge forces limit the device efficiency due to saturation of the axial bunching, in the pasotron they do not destroy electron bunches but cause the radial expansion of them, which may increase device efficiency. The role of these forces is compared with the ion focusing and the radial electric field of the wave, and it is shown that, under certain conditions, it may dominate. The efficiency of the pasotron-TWT with a phase-mixed beam well focused at the entrance may exceed 50%. In the pasotron-BWO, the efficiency is lower (up to 26% in the case studied), but it can grow as the equivalent of the Pierce gain parameter increases.
Computation of non-linear acoustics in two-dimensional blade-vortex interactions
NASA Technical Reports Server (NTRS)
Baeder, J. D.
1987-01-01
The propagation characteristics of the interaction between a vortex and a helicopter airfoil are investigated by a variety of methods, and a comparison is made between solutions to the linearized transonic small disturbance equation, transonic small disturbance equation, Euler equations, and Navier-Stokes equations. Although the first two methods are able to accurately predict the propagation of acoustic waves, they are unable to accurately describe the initial formation of acoustic waves. The Euler and Navier-Stokes equations are shown to be well suited to the investigation of acoustic waves and give approximately the same results.
Weiren Chou and Akira Takagi
2003-02-24
This paper introduces a new method for stacking beams in the longitudinal phase space. It uses RF barriers to confine and compress beams in an accelerator, provided that the machine momentum acceptance is a few times larger than the momentum spread of the injected beam. This is the case for the Fermilab Main Injector. A barrier RF system employing Finemet cores and high-voltage solid-state switches is under construction. The goal is to double the number of protons per cycle on the production target for Run2 and NuMI experiments.
Nonlinear fluid-structure interaction in a flexible shelter under blast loading
NASA Astrophysics Data System (ADS)
Chun, Sangeon
Recently, numerous flexible structures have been employed in various fields of industry. Loading conditions sustained by these flexible structures are often not described well enough for engineering analyses even though these conditions are important. Here, a flexible tent with an interior Collective Protection System, which is subjected to an explosion, is analyzed. The tent protects personnel from biological and chemical agents with a pressurized liner inside the tent as an environmental barrier. Field tests showed unexpected damage to the liner, and most of the damage occurred on tent's leeward side. To solve this problem, various tests and analyses have been performed, involving material characteristics of the liner, canvas, and zip seals, modeling of the blast loading over the tent and inside the tent, and structural response of the tent to the blast loading as collaborative research works with others. It was found that the blast loading and the structural response can not be analyzed separately due to the interaction between the flexible structure and the dynamic pressure loading. In this dissertation, the dynamic loadings imposed on both the interior and the exterior sides of the tent structure due to the airblasts and the resulting dynamic responses were studied. First, the blast loadings were obtained by a newly proposed theoretical method of analytical/empirical models which was developed into a FORTRAN program. Then, a numerical method of an iterative Fluid-Structure Interaction using Computational Fluid Dynamics and Computational Structural Dynamics was employed to simulate the blast wave propagation inside and outside the flexible structure and to calculate the dynamic loads on it. All the results were compared with the field test data conducted by the Air Force Research Laboratory. The experimental pressure data were gathered from pressure gauges attached to the tent surfaces at different locations. The comparison showed that the proposed methods can
NASA Astrophysics Data System (ADS)
Zhang, Luning
Solid-liquid interfaces have been the focus of different communities of scientists due to its importance in industrial applications and chemical processes in nature. Molecular interactions and surface charges affect the physicochemical properties of these interfaces and a thorough understanding is still lacking now. This thesis describes our work in studying several model solid-liquid interfaces using sum-frequency vibrational spectroscopy. Through the studies of interfacial vibrational spectra, we hope to gain better understanding of molecular interactions in competitive adsorption process and also surface charging behavior at different pH and salt concentrations. We start by studying alcohol-water mixture and the adsorption behavior at both hydrophilic and hydrophobic surfaces. In both cases, alcohol adsorbs preferentially from water. The tendency for water to form strong hydrogen-bonding network is the driving force for preferential adsorption of alcohol. We proposed two different interfacial molecular structures on hydrophilic and hydrophobic surfaces. We move on to study the interaction of pure water with a solid surface. Single crystal alumina is used as a model system. At different pH, the surface can undergo protonation and deprotonation reactions and accumulates surface charge. Both the hydrogen-bonding with water and the surface field created by surface charge can affect interfacial water structure. Combining the information obtained with intensity and phase spectra, we find water molecules have two types of bonding within the interfacial layer: weakly hydrogen-bonded species near 3450 cm-1 that does not flip with switching surface charge, and strongly hydrogen-bonded species at 3200 cm-1 that readily flips with switching surface field. One other system we have studied is nanoporous silica-water interface. We found that signal from interfacial water is reduced due to the porous nature of the film. The water spectral features tell us about the interfacial
Nonlinear fluid/structure interaction relating a rupture-disc pressure-relief device. [LMFBR
Hsieh, B.J.; Kot, C.A.; Shin, Y.W.; Youngdahl, C.K.
1983-01-01
Rupture disc assemblies are used in piping network systems as a pressure-relief device. The reverse-buckling type is chosen for application in a liquid metal fast breeder reactor. This assembly is used successfully in systems in which the fluid is highly compressible, such as air; the opening up of the disc by the knife setup is complete. However, this is not true for a liquid system; it had been observed experimentally that the disc may open up only partially or not at all. Therefore, to realistically understand and represent a rupture disc assembly in a liquid environment, the fluid-structure interactions between the liquid medium and the disc assembly must be considered. The methods for analyzing the fluid and the disc and the mechanism interconnecting them are presented. The fluid is allowed to cavitate through a column-cavitation model and the disc is allowed to become plastically deformed through the classic Von Mises' yield criteria, when necessary.
Nonlinear Dynamics of Emotion-Cognition Interaction: When Emotion Does not Destroy Cognition?
Afraimovich, Valentin; Young, Todd; Muezzinoglu, Mehmet K.; Rabinovich, Mikhail I.
2011-01-01
Emotion (i.e., spontaneous motivation and subsequent implementation of a behavior) and cognition (i.e., problem solving by information processing) are essential to how we, as humans, respond to changes in our environment. Recent studies in cognitive science suggest that emotion and cognition are subserved by different, although heavily integrated, neural systems. Understanding the time-varying relationship of emotion and cognition is a challenging goal with important implications for neuroscience. We formulate here the dynamical model of emotion-cognition interaction that is based on the following principles: (1) the temporal evolution of cognitive and emotion modes are captured by the incoming stimuli and competition within and among themselves (competition principle); (2) metastable states exist in the unified emotion-cognition phase space; and (3) the brain processes information with robust and reproducible transients through the sequence of metastable states. Such a model can take advantage of the often ignored temporal structure of the emotion-cognition interaction to provide a robust and generalizable method for understanding the relationship between brain activation and complex human behavior. The mathematical image of the robust and reproducible transient dynamics is a Stable Heteroclinic Sequence (SHS), and the Stable Heteroclinic Channels (SHCs). These have been hypothesized to be possible mechanisms that lead to the sequential transient behavior observed in networks. We investigate the modularity of SHCs, i.e., given a SHS and a SHC that is supported in one part of a network, we study conditions under which the SHC pertaining to the cognition will continue to function in the presence of interfering activity with other parts of the network, i.e., emotion. PMID:20821062
Linear and nonlinear wave-particle interactions. Ph.D. Thesis
Ho, A.Y.
1994-12-31
In part 1, a quasi-particle approach is adopted to examine the effect of ionospheric irregularities on the propagation of beacon satellite signals through the ionosphere. The experimental data corresponding to the Bottomside Sinusoidal (BSS) irregularity is used to validate the approach. Good agreement in the scintillation index S4 is found. It is demonstrated that a traveling BSS irregularity can indeed cause a scintillation in the transionospheric signal in agreement with the experimental measurements. The theory is then used to make a prediction for future experimental observations. In part 2, the authors show that when an energetic proton originally trapped by the geomagnetic mirror field near the equator interacts with a Kinetic Alfven Wave (KAW), its trajectory may become chaotic. As a result of this chaotic motion, the proton will escape from its confines and either precipitate into the polar region or drift downward into the lower altitude region. A cyclotron average is first used to reduce the number of degrees of freedom of the system from 2.5 to 1.5 so that the chaoticity of the system can be revealed by Poincare surface of section method. Next, a Lyapunov exponent analysis for limited cases of initial conditions provides a quantitative measure of chaos. In the chaotic region, the longitudinal motion of the proton is shown to involve irregular oscillation in excursion amplitude leading to proton diffusion into the loss cone. The proton also drifts radially via a nonzero average E x B drift velocity acquired in the interaction with the wave. In part 3, an experiment is performed to study the electromagnetic wave absorption and scattering properties of the structured and lossy plasma for use in a radar cloaking device. Measurements of microwave attenuation and scattering by a hollow cathode produced plasma column show greater than 20 dB attenuation in transmission for wave frequency range of 3.5 to 11 GHz.
NASA Astrophysics Data System (ADS)
Fine, S.; Shanks, T.; Green, P.; Kelly, B. C.; Croom, S. M.; Webster, R. L.; Berger, E.; Chornock, R.; Burgett, W. S.; Chambers, K. C.; Kaiser, N.; Price, P. A.
2013-07-01
Over the past 20 years reverberation mapping has proved one of the most successful techniques for studying the local (<1 pc) environment of supermassive black holes that drive active galactic nuclei. Key successes of reverberation mapping have been direct black hole mass estimates, the radius-luminosity relation for the Hβ line and the calibration of single-epoch mass estimators commonly employed up to z ˜ 7. However, observing constraints mean that few studies have been successful at z > 0.1, or for the more-luminous quasars that make up the majority of current spectroscopic samples, or for rest-frame ultraviolet emission lines available in optical spectra of z > 0.5 objects. Previously, we described a technique for stacking cross-correlations to obtain reverberation mapping results at high z. Here, we present the first results from a campaign designed for this purpose. We construct stacked cross-correlation functions for the C IV and Mg II lines and find a clear peak in both. We find that the peak in the Mg II correlation is at longer lags than C IV consistent with previous results at low redshift. For the C IV sample, we are able to bin by luminosity and find evidence for increasing lags for more-luminous objects. This C IV radius-luminosity relation is consistent with previous studies but with a fraction of the observational cost.
Asymmetric Flexible Supercapacitor Stack
2008-01-01
Electrical double layer supercapacitor is very significant in the field of electrical energy storage which can be the solution for the current revolution in the electronic devices like mobile phones, camera flashes which needs flexible and miniaturized energy storage device with all non-aqueous components. The multiwalled carbon nanotubes (MWNTs) have been synthesized by catalytic chemical vapor deposition technique over hydrogen decrepitated Mischmetal (Mm) based AB3alloy hydride. The polymer dispersed MWNTs have been obtained by insitu polymerization and the metal oxide/MWNTs were synthesized by sol-gel method. Morphological characterizations of polymer dispersed MWNTs have been carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM and HRTEM). An assymetric double supercapacitor stack has been fabricated using polymer/MWNTs and metal oxide/MWNTs coated over flexible carbon fabric as electrodes and nafion®membrane as a solid electrolyte. Electrochemical performance of the supercapacitor stack has been investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.
Stacked Extreme Learning Machines.
Zhou, Hongming; Huang, Guang-Bin; Lin, Zhiping; Wang, Han; Soh, Yeng Chai
2015-09-01
Extreme learning machine (ELM) has recently attracted many researchers' interest due to its very fast learning speed, good generalization ability, and ease of implementation. It provides a unified solution that can be used directly to solve regression, binary, and multiclass classification problems. In this paper, we propose a stacked ELMs (S-ELMs) that is specially designed for solving large and complex data problems. The S-ELMs divides a single large ELM network into multiple stacked small ELMs which are serially connected. The S-ELMs can approximate a very large ELM network with small memory requirement. To further improve the testing accuracy on big data problems, the ELM autoencoder can be implemented during each iteration of the S-ELMs algorithm. The simulation results show that the S-ELMs even with random hidden nodes can achieve similar testing accuracy to support vector machine (SVM) while having low memory requirements. With the help of ELM autoencoder, the S-ELMs can achieve much better testing accuracy than SVM and slightly better accuracy than deep belief network (DBN) with much faster training speed. PMID:25361517
Can Dispersion Forces Govern Aromatic Stacking in an Organic Solvent?
Yang, Lixu; Brazier, John B; Hubbard, Thomas A; Rogers, David M; Cockroft, Scott L
2016-01-18
Experimental support for the dominance of van der Waals dispersion forces in aromatic stacking interactions occurring in organic solution is surprisingly limited. The size-dependence of aromatic stacking in an organic solvent was examined. The interaction energy was found to vary by about 7.5 kJ mol(-1) on going from a phenyl-phenyl to an anthracene-pyrene stack. Strikingly, the experimental data were highly correlated with dispersion energies determined using symmetry-adapted perturbation theory (SAPT), while the induction, exchange, electrostatic, and solvation energy components correlated poorly. Both the experimental data and the SAPT-dispersion energies gave high-quality correlations with the change in solvent accessible area upon complexation. Thus, the size-dependence of aromatic stacking interactions is consistent with the dominance of van der Waals dispersion forces even in the presence of a competing polarizable solvent. PMID:26632979
Atmospheric infrasound from nonlinear wave interactions during Hurricanes Felicia and Neki of 2009
NASA Astrophysics Data System (ADS)
Stopa, Justin E.; Cheung, Kwok Fai; GarcéS, Milton A.; Badger, Nickles
2012-12-01
Monitoring stations around the globe routinely detect microbarom signals with a dominant frequency of ˜0.2 Hz from regions of marine storminess. International Monitoring System (IMS) infrasound array IS59 in Kailua-Kona, Hawaii recorded clear signals in close proximity of Hurricanes Felicia and Neki of 2009 for a first-hand investigation of the detailed source mechanism through a hindcast analysis. A spectral wave model describes the tropical cyclone and ambient sea states through a system of two-way nested grids with forcing from a blended data set of global, regional, and cyclonic winds. The computed wave conditions are validated with altimetry measurements and utilized in an acoustic model to estimate the intensity and spatial distribution of the microbarom source. The model results elucidate origins of infrasound signals from the tropical cyclone waves as well as their interactions with the ambient conditions consisting of swells, wind seas, and storm waves from nearby systems. The positive correlation between the IS59 observations and the theoretical microbarom estimates, and the saturation of recorded signals from high-energy sources support the use of infrasound signals for inference of tropical cyclone waves.
Nonlinear fluid/structure interaction relating a rupture-disc pressure-relief device
Hsieh, B.J.; Kot, C.A.; Shin, Y.W.; Youngdahi, C.K.
1983-01-01
Rupture disc assemblies are used in piping network systems as pressure-relief devices. The reverse-buckling type discs are chosen for application in heat transport systems of liquid metal fast breeder reactors. When the pressure on the disc is of sufficient magnitude and duration, the disc develops large displacement, is consequently torn open by a cutting-knife setup and thus relieves the excess pressure. Such disc assemblies are used very successfully in systems in which the fluid is highly compressible, e.g., air; the opening of the disc by the knife setup is complete. However, this is not true for a liquid system; in this case it has been observed experimentally that the disc may open up only partially or not at all. Therefore, to understand and realistically represent a rupture disc assembly in a liquid environment, the fluid-structure interactions between the liquid medium and the disc assembly must be considered. In this paper, methods for analyzing the fluid and the disc and the mechanism interconnecting them are presented. When necessary the fluid is allowed to cavitate through a column separation model and the disc can become plastically deformed using the classic Von Mises' yield criteria.
NASA Technical Reports Server (NTRS)
Dietrich, David E.; Mehra, Avichal; Haney, Robert L.; Bowman, Malcolm J.; Tseng, Yu-Heng
2003-01-01
Gulf Stream (GS) separation near its observed Cape Hatteras (CH) separation location, and its ensuing path and dynamics, is a challenging ocean modeling problem. If a model GS separates much farther north than CH, then northward GS meanders, which pinch off warm core eddies (rings), are not possible or are strongly constrained by the Grand Banks shelfbreak. Cold core rings pinch off the southward GS meanders. The rings are often re-absorbed by the GS. The important warm core rings enhance heat exchange and, especially, affect the northern GS branch after GS bifurcation near the New England Seamount Chain. This northern branch gains heat by contact with the southern branch water upstream of bifurcation, and warms the Arctic Ocean and northern seas, thus playing a major role in ice dynamics, thermohaline circulation and possible global climate warming. These rings transport heat northward between the separated GS and shelf slope/Deep Western Boundary Current system (DWBC). This region has nearly level time mean isopycnals. The eddy heat transport convergence/divergence enhances the shelfbreak and GS front intensities and thus also increases watermass transformation. The fronts are maintained by warm advection by the Florida Current and cool advection by the DWBC. Thus, the GS interaction with the DWBC through the intermediate eddy field is climatologically important.
NASA Astrophysics Data System (ADS)
Wang, Qi-Min; Gao, Yi-Tian; Su, Chuan-Qi; Mao, Bing-Qing; Gao, Zhe; Yang, Jin-Wei
2015-12-01
In this paper, a higher-order (2 + 1) -dimensional nonlinear Schrödinger-type equation is investigated, which describes the nonlinear spin dynamics of the (2 + 1) -dimensional Heisenberg ferromagnetic spin chain with bilinear and biquadratic interaction. Lax pair and infinite-number conservation laws are constructed, which could prove the existence of the multi-soliton solutions. Via the auxiliary function, bilinear forms and dark-soliton solutions are derived. Properties and interaction patterns for the dark solitons are investigated: (i) Effects on the dark solitons arising from the bilinear interaction, biquadratic interaction and lattice parameter are discussed. (ii) Through the asymptotic analysis, elastic and inelastic interaction between the two solitons is discussed analytically and graphically, respectively. Due to the elastic interaction, amplitudes and velocities of the two dark solitons remain unchanged with the distortion of the interaction area, except for certain phase shifts. However, in virtue of the inelastic interaction, amplitudes of the dark solitons reduce to zero, without the distortion. (iii) Elastic interaction among the three dark solitons is investigated, which implies that the properties of the elastic interaction among the three are similar to that between the two, except for the more complicated distortion. Inelastic-elastic interaction is also investigated, which implies that the interaction between the inelastic region and the dark soliton is elastic. (iv) Linear stability analysis is proposed, which is used to analyze the properties of modulation instability and proves that the dark solitons are modulationally stable.
NASA Technical Reports Server (NTRS)
Bayliss, A.; Maestrello, L.; Turkel, E.
1985-01-01
The fluctuating field of a jet excited by transient mass injection is simulated numerically. The model is developed by expanding the state vector as a mean state plus a fluctuating state. Nonlinear terms are not neglected, and the effect of nonlinearity was studied. A high order numerical method is used to compute the solution. The results show a significant spectral broadening in the flow field due to the nonlinearity. In addition, large scale structures are broken down into smaller scales.
Stacked insulator induction accelerator gaps
Houck, T.I.; Westenskow, G.A.; Kim, J.S.; Eylon, S.; Henestroza, E.; Yu, S.S.; Vanecek, D.
1997-05-01
Stacked insulators, with alternating layers of insulating material and conducting film, have been shown to support high surface electrical field stresses. We have investigated the application of the stacked insulator technology to the design of induction accelerator modules for the Relativistic-Klystron Two-Beam Accelerator program. The rf properties of the accelerating gaps using stacked insulators, particularly the impedance at frequencies above the beam pipe cutoff frequency, are investigated. Low impedance is critical for Relativistic-Klystron Two-Beam Accelerator applications where a high current, bunched beam is trsnsported through many accelerating gaps. An induction accelerator module designs using a stacked insulator is presented.
Thermoacoustic pin stacks. Summary report
Keolian, R.M.
1994-07-06
The construction and testing of a new stack geometry for thermoacoustic engines, called a pin stack, has been started. The stack is at the heart of a class of heat engines that use sound to deliver refrigeration, or use a temperature difference to generate sound. Calculations show that the pin stack should make useful improvements in engine efficiency. About 2000 wires will be hand sewn in a hexagonal lattice between the hot and cold heat exchangers in a sound source using low pressure neon gas between 300 K and 77 K. Thermoacoustics, Refrigeration, Acoustic source, Heat pump.
NASA Astrophysics Data System (ADS)
Kumar, Santosh; Raychowdhury, Prishati; Gundlapalli, Prabhakar
2015-06-01
Design of critical facilities such as nuclear power plant requires an accurate and precise evaluation of seismic demands, as any failure of these facilities poses immense threat to the community. Design complexity of these structures reinforces the necessity of a robust 3D modeling and analysis of the structure and the soil-foundation interface. Moreover, it is important to consider the multiple components of ground motion during time history analysis for a realistic simulation. Present study is focused on investigating the seismic response of a nuclear containment structure considering nonlinear Winkler-based approach to model the soil-foundation interface using a distributed array of inelastic springs, dashpots and gap elements. It is observed from this study that the natural period of the structure increases about 10 %, whereas the force demands decreases up to 24 % by considering the soil-structure interaction. Further, it is observed that foundation deformations, such as rotation and sliding are affected by the embedment ratio, indicating an increase of up to 56 % in these responses for a reduction of embedment from 0.5 to 0.05× the width of the footing.
NASA Astrophysics Data System (ADS)
Lee, Jaehyun; Yun, Gunsu S.; Choi, Minjun J.; Kwon, Jae-Min; Jeon, Young-Mu; Lee, Woochang; Luhmann, Neville C.; Park, Hyeon K.
2016-08-01
The effect of static n =1 resonant magnetic perturbation (RMP) on the spatial structure and temporal dynamics of edge-localized modes (ELMs) and edge turbulence in tokamak plasma has been investigated. Two-dimensional images measured by a millimeter-wave camera on the KSTAR tokamak revealed that the coherent filamentary modes (i.e., ELMs) are still present in the edge region when the usual large scale collapse of the edge confinement, i.e., the ELM crash, is completely suppressed by n =1 RMP. Cross-correlation analyses on the 2D images show that (1) the RMP enhances turbulent fluctuations in the edge toward the ELM-crash-suppression phase, (2) the induced turbulence has a clear dispersion relation for wide ranges of wave number and frequency, and (3) the turbulence involves a net radially outward energy transport. Nonlinear interactions of the turbulent eddies with the coexisting ELMs are clearly observed by bispectral analysis, which implies that the exchange of energy between them may be the key to the prevention of large scale crashes.
Ovtchinnikov, Mikhail; Easter, Richard C.
2009-02-01
Monotonicity constraints and gradient preserving flux corrections employed by many advection algorithms used in atmospheric models make these algorithms non-linear. Consequently, any relations among model variables transported separately are not necessarily preserved in such models. These errors cannot be revealed by traditional algorithm testing based on advection of a single tracer. New type of tests are developed and conducted to evaluate the preservation of a sum of several number mixing ratios advected independently of each other, as is the case, for example, in models using bin or sectional representation of aerosol or cloud particle size distribution. The tests show that when three tracers are advected in 1D uniform constant velocity flow, local errors in the sum can be on the order of 10%. When cloud-like interactions are allowed among the tracers, errors in total sum of three mixing ratios can reach up to 30%. Several approaches to eliminate the error are suggested, all based on advecting the sum as a separate variable and then normalizing mixing ratios for individual tracers to match the total sum. A simple scalar normalization preserves the total number mixing ratio and positive definiteness of the variables but the monotonicity constraint for individual tracers is no longer maintained. More involved flux normalization procedures are developed for the flux based advection algorithms to maintain the monotonicity for individual scalars and their sum.
NASA Astrophysics Data System (ADS)
Stokes, G. Y.; Buchbinder, A. M.; Gibbs-Davis, J. M.; Scheidt, K. A.; Geiger, F. M.
2008-12-01
Terpenes emitted from vegetation can become oxidized and form molecular films on tropospheric aerosols. These greasy olefinic coatings can be oxidized by ozone and may influence the microphysics of cloud formation and the earth's climate. Using a laboratory approach that combines organic synthesis with nonlinear optical spectroscopy, we utilized vibrational broadband sum frequency generation (SFG) to survey a number of terpene-modified glass surfaces and track their interactions with ozone in real time. Exposure of these surfaces to tropospherically relevant amounts of ozone at 1 atm total pressure and 296 K yield initial reactive uptake coefficients that are significantly higher than those measured in corresponding gas phase reactions and correlate with the accessibility of the C=C double bonds at the surface. The intensity changes in the olefinic =C-H stretch and aliphatic C-H stretching region of surface vibrational spectra were used to characterize surface-bound product species. Combined with a histogram analysis of contact angle measurements carried out before and after ozonolysis, our kinetic and spectroscopic studies suggest a reaction pathway involving vibrationally hot Criegee intermediates that strongly compete with pathways that involve thermalized surface species, a chemical insight which may help reduce uncertainties associated with aerosols when included in global climate change models.
Yamanaka, Tsuyuko; Raffaelli, David; White, Piran C. L.
2013-01-01
Sea-level rise induced by climate change may have significant impacts on the ecosystem functions and ecosystem services provided by intertidal sediment ecosystems. Accelerated sea-level rise is expected to lead to steeper beach slopes, coarser particle sizes and increased wave exposure, with consequent impacts on intertidal ecosystems. We examined the relationships between abundance, biomass, and community metabolism of benthic fauna with beach slope, particle size and exposure, using samples across a range of conditions from three different locations in the UK, to determine the significance of sediment particle size beach slope and wave exposure in affecting benthic fauna and ecosystem function in different ecological contexts. Our results show that abundance, biomass and oxygen consumption of intertidal macrofauna and meiofauna are affected significantly by interactions among sediment particle size, beach slope and wave exposure. For macrofauna on less sloping beaches, the effect of these physical constraints is mediated by the local context, although for meiofauna and for macrofauna on intermediate and steeper beaches, the effects of physical constraints dominate. Steeper beach slopes, coarser particle sizes and increased wave exposure generally result in decreases in abundance, biomass and oxygen consumption, but these relationships are complex and non-linear. Sea-level rise is likely to lead to changes in ecosystem structure with generally negative impacts on ecosystem functions and ecosystem services. However, the impacts of sea-level rise will also be affected by local ecological context, especially for less sloping beaches. PMID:23861863
NASA Astrophysics Data System (ADS)
Heinrich, Hora; Cang, Yu; He, Xiantu; Zhang, Jie; F, Osman; J, Badziak; F, P. Boody; S, Gammino; R, Höpfl; K, Jungwirth; B, Kralikova; J, Kraska; L, Laska; Liu, Hong; G, H. Miley; P, Parys; Peng, Hansheng; M, Pfeifer; K, Rohlena; J, Skala; Z, Skladanowski; L, Torrisi; J, Ullschmied; J, Wolowski; Zhang, Weiyan
2004-02-01
The discovery of the essential difference of maximum ion energy for TW - ps laser plasma interaction compared with the 100 ns laser pulses [1] led to the theory of a skin layer model [2] where the control of prepulses suppressed the usual relativistic self-focusing. The subsequent generation of two nonlinear force driven blocks has been demonstrated experimentally and in extensive numerical studies where one block moves against the laser light and the other block into the irradiated target. These blocks of nearly solid state density DT plasma correspond to ion beam current densities [3] exceeding 1010 A/cm2 where the ion velocity can be chosen up to highly relativistic values. Using the results of the expected ignition of DT fuel by light ion beams, a self-sustained fusion reaction front may be generated even into uncompressed solid DT fuel similar to the Nuckolls-Wood [4] scheme where 10 kJ laser pulses produce 100 MJ fusion energy. This new and simplified scheme of laser-ICF needs and optimisation of the involved parameters.
Lee, Jaehyun; Yun, Gunsu S; Choi, Minjun J; Kwon, Jae-Min; Jeon, Young-Mu; Lee, Woochang; Luhmann, Neville C; Park, Hyeon K
2016-08-12
The effect of static n=1 resonant magnetic perturbation (RMP) on the spatial structure and temporal dynamics of edge-localized modes (ELMs) and edge turbulence in tokamak plasma has been investigated. Two-dimensional images measured by a millimeter-wave camera on the KSTAR tokamak revealed that the coherent filamentary modes (i.e., ELMs) are still present in the edge region when the usual large scale collapse of the edge confinement, i.e., the ELM crash, is completely suppressed by n=1 RMP. Cross-correlation analyses on the 2D images show that (1) the RMP enhances turbulent fluctuations in the edge toward the ELM-crash-suppression phase, (2) the induced turbulence has a clear dispersion relation for wide ranges of wave number and frequency, and (3) the turbulence involves a net radially outward energy transport. Nonlinear interactions of the turbulent eddies with the coexisting ELMs are clearly observed by bispectral analysis, which implies that the exchange of energy between them may be the key to the prevention of large scale crashes. PMID:27563970
NASA Astrophysics Data System (ADS)
Geiges, A.; Nowak, W.; Rubin, Y.
2013-12-01
Stochastic models of sub-surface systems generally suffer from parametric and conceptual uncertainty. To reduce the model uncertainty, model parameters are calibrated using additional collected data. These data often come from costly data acquisition campaigns that need to be optimized to collect the data with the highest data utility (DU) or value of information. In model-based approaches, the DU is evaluated based on the uncertain model itself and is therefore uncertain as well. Additionally, for non-linear models, data utility depends on the yet unobserved measurement values and can only be estimated as an expected value over an assumed distribution of possible measurement values. Both factors introduce uncertainty into the optimization of field campaigns. We propose and investigate a sequential interaction scheme between campaign optimization, data collection and model calibration. The field campaign is split in individual segments. Each segment consists of optimization, segment-wise data collection, and successive model calibration or data assimilation. By doing so, (1) the expected data utility for the newly collected data is replaced by their actual one, (2) the calibration restricts both conceptual and parametric model uncertainty, and thus (3) the distribution of possible future data values for the subsequent campaign segments also changes. Hence, the model to describe the real system improves successively with each collected data segment, and so does the estimate of the yet remaining data requirements to achieve the overall investigation goals. We will show that using the sequentially improved model for the optimal design (OD) of the remaining field campaign leads to superior and more targeted designs.However, this traditional sequential OD optimizes small data segments one-by-one. In such a strategy, possible mutual dependencies with the possible data values and the optimization of data values collection in later segments are neglected. This allows a
NASA Astrophysics Data System (ADS)
Baghshahi, H. R.; Tavassoly, M. K.; Behjat, A.
2016-04-01
In this paper, we investigate the entanglement of a non-degenerate Diamond-type four-level atom interacting with a single-mode cavity field with multi-photon transitions in the intensity-dependent (atom-field) coupling regime. We consider the non-degenerate atom in the intermediate levels and with different detunings between the frequencies of the atom and quantized light field. The decay of the atom from the topmost state to the two intermediate states and also that from the two intermediate states to the bottom state are taken into account. In spite of the fact that the system seems to be complicated, the explicit form of the state vector of the entire system is analytically obtained by using the Laplace transform technique. Then, the entanglement between the atom and field is evaluated with the help of I concurrence measure. The effects of intensity-dependent coupling, decay rates, multi-photon processes and detuning parameters on the concurrence are numerically analyzed, in detail. The results indicate that, the larger the decay coefficients, the more rapid the entanglement decrement between the atom and the field. The intensity-dependent coupling enhances the entanglement between atom and field in most of the interaction times. Furthermore, the degeneracy of the intermediate atomic levels in the presence of decay parameters increases the asymptotic value of the concurrence in the linear and nonlinear regimes. Finally, the amount of entanglement between atom and field in the presence of decay parameters for two-photon transition is greater than that for the one-photon transition.
NASA Astrophysics Data System (ADS)
Lauterborn, Werner; Kurz, Thomas; Akhatov, Iskander
At high sound intensities or long propagation distances at
NASA Astrophysics Data System (ADS)
Jenness, Timothy; LSST Data Management Team
2016-01-01
The Large Synoptic Survey Telescope (LSST) is an 8-m optical ground-based telescope being constructed on Cerro Pachon in Chile. LSST will survey half the sky every few nights in six optical bands. The data will be transferred to the data center in North America and within 60 seconds it will be reduced using difference imaging and an alert list be generated for the community. Additionally, annual data releases will be constructed from all the data during the 10-year mission, producing catalogs and deep co-added images with unprecedented time resolution for such a large region of sky. In the paper we present the current status of the LSST stack including the data processing components, Qserv database and data visualization software, describe how to obtain it, and provide a summary of the development road map.
Energy Science and Technology Software Center (ESTSC)
2008-01-16
STAT is a light weight debugging tool that gathers and merges stack traces from all of the processes in a parallel application. STAT uses the MRNet free based overlay network to broadcast commands from the tool front-end to the STAT daemons and for the front-end to gather the traces from the STAT daemons. As the traces propagate through the MRNet network tree, they are merged across all tasks to form a single call prefix tree.more » The call prefix tree can be examined to identify tasks with similar function call patterns and to delineate a small set of equivalence classes. A representative task from each of these classes can then be fed into a full feature debugger like TotalView for root cause analysis.« less
Energy Science and Technology Software Center (ESTSC)
2013-02-19
STAT is a light weight debugging tool that gathers and merges stack traces from all of the processes in a parallell application. STAT uses the MRNet tree based overlay network to broadcast commands from the tool front-end to the STAT daemons and for the front-end to gather the traces from the STAT daemons. As the traces propagate through the MRNet network tree, they are merged across all tasks to from a single call prefix tree.more » The call prefix tree can be examined to identify tasks with similar function call patterns and to delineate a small set of equivalence slasses. A representative task from each of these classes can then be fed into a full feature debugger like TotalView for root cause analysis.« less
2013-02-19
STAT is a light weight debugging tool that gathers and merges stack traces from all of the processes in a parallell application. STAT uses the MRNet tree based overlay network to broadcast commands from the tool front-end to the STAT daemons and for the front-end to gather the traces from the STAT daemons. As the traces propagate through the MRNet network tree, they are merged across all tasks to from a single call prefix tree. The call prefix tree can be examined to identify tasks with similar function call patterns and to delineate a small set of equivalence slasses. A representative task from each of these classes can then be fed into a full feature debugger like TotalView for root cause analysis.
2008-01-16
STAT is a light weight debugging tool that gathers and merges stack traces from all of the processes in a parallel application. STAT uses the MRNet free based overlay network to broadcast commands from the tool front-end to the STAT daemons and for the front-end to gather the traces from the STAT daemons. As the traces propagate through the MRNet network tree, they are merged across all tasks to form a single call prefix tree. The call prefix tree can be examined to identify tasks with similar function call patterns and to delineate a small set of equivalence classes. A representative task from each of these classes can then be fed into a full feature debugger like TotalView for root cause analysis.
Zigzag stacks and m-regular linear stacks.
Chen, William Y C; Guo, Qiang-Hui; Sun, Lisa H; Wang, Jian
2014-12-01
The contact map of a protein fold is a graph that represents the patterns of contacts in the fold. It is known that the contact map can be decomposed into stacks and queues. RNA secondary structures are special stacks in which the degree of each vertex is at most one and each arc has length of at least two. Waterman and Smith derived a formula for the number of RNA secondary structures of length n with exactly k arcs. Höner zu Siederdissen et al. developed a folding algorithm for extended RNA secondary structures in which each vertex has maximum degree two. An equation for the generating function of extended RNA secondary structures was obtained by Müller and Nebel by using a context-free grammar approach, which leads to an asymptotic formula. In this article, we consider m-regular linear stacks, where each arc has length at least m and the degree of each vertex is bounded by two. Extended RNA secondary structures are exactly 2-regular linear stacks. For any m ≥ 2, we obtain an equation for the generating function of the m-regular linear stacks. For given m, we deduce a recurrence relation and an asymptotic formula for the number of m-regular linear stacks on n vertices. To establish the equation, we use the reduction operation of Chen, Deng, and Du to transform an m-regular linear stack to an m-reduced zigzag (or alternating) stack. Then we find an equation for m-reduced zigzag stacks leading to an equation for m-regular linear stacks. PMID:25455155
Research in nonlinear structural and solid mechanics
NASA Technical Reports Server (NTRS)
Mccomb, H. G., Jr. (Compiler); Noor, A. K. (Compiler)
1980-01-01
Nonlinear analysis of building structures and numerical solution of nonlinear algebraic equations and Newton's method are discussed. Other topics include: nonlinear interaction problems; solution procedures for nonlinear problems; crash dynamics and advanced nonlinear applications; material characterization, contact problems, and inelastic response; and formulation aspects and special software for nonlinear analysis.
Assessing Elementary Algebra with STACK
ERIC Educational Resources Information Center
Sangwin, Christopher J.
2007-01-01
This paper concerns computer aided assessment (CAA) of mathematics in which a computer algebra system (CAS) is used to help assess students' responses to elementary algebra questions. Using a methodology of documentary analysis, we examine what is taught in elementary algebra. The STACK CAA system, http://www.stack.bham.ac.uk/, which uses the CAS…
NASA Astrophysics Data System (ADS)
Lee, Young-Hyun; Kim, Jonghyeon; Yoo, Seungyeol
2016-09-01
The critical cell voltage drop in a stack can be followed by stack defect. A method of detecting defective cell is the cell voltage monitoring. The other methods are based on the nonlinear frequency response. In this paper, the superposition principle for the diagnosis of PEMFC stack is introduced. If critical cell voltage drops exist, the stack behaves as a nonlinear system. This nonlinearity can explicitly appear in the ohmic overpotential region of a voltage-current curve. To detect the critical cell voltage drop, a stack is excited by two input direct test-currents which have smaller amplitude than an operating stack current and have an equal distance value from the operating current. If the difference between one voltage excited by a test current and the voltage excited by a load current is not equal to the difference between the other voltage response and the voltage excited by the load current, the stack system acts as a nonlinear system. This means that there is a critical cell voltage drop. The deviation from the value zero of the difference reflects the grade of the system nonlinearity. A simulation model for the stack diagnosis is developed based on the SPP, and experimentally validated.
49 CFR 178.815 - Stacking test.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 49 Transportation 3 2013-10-01 2013-10-01 false Stacking test. 178.815 Section 178.815... Stacking test. (a) General. The stacking test must be conducted for the qualification of all IBC design types intended to be stacked. (b) Special preparation for the stacking test. (1) All IBCs...
NASA Astrophysics Data System (ADS)
Baghshahi, H. R.; Tavassoly, M. K.
2015-03-01
In this paper, we present a model which exhibits two identical Ξ-type three-level atoms interacting with a single-mode field with k-photon transition in an optical cavity enclosed by a Kerr medium. Considering full nonlinear formalism, it is assumed that the single-mode field, atom-field coupling and Kerr medium are all f-deformed. By using the adiabatic elimination method, it is shown that, the Hamiltonian of the considered system can be reduced to an effective Hamiltonian with two two-level atoms and f-deformed Stark shift. In spite of the fact that, the system seems to be complicated, under initial conditions which may be prepared for the atoms (coherent superposition of their ground and upper states) and the field (coherent state), the explicit form of the state vector of the entire system is analytically obtained. Then, the entanglement dynamics between different subsystems ( i.e. "field-two atoms", "atom-(field+atom)" and "atom-atom") are evaluated through appropriate measures like von Neumann entropy, tangle and concurrence. In addition, the effects of intensity-dependent coupling, deformed Kerr medium, detuning parameter, deformed Stark shift and multi-photon process on the considered entanglement measures are numerically analyzed, in detail. It is shown that the degree of entanglement between subsystems can be controlled by selecting the evolved parameters, suitably. Briefly, the Kerr medium highly decreases the amount of different considered measures of entanglement, especially for two-photon transition. This destructive effect preserves even when all other parameters are present, too. Furthermore, we find that the so-called entanglement sudden death and birth can occur in the atom-atom entanglement.
Yamashita, Yui; Kadokura, Yoshitomo; Sotta, Naoyuki; Fujiwara, Toru; Takigawa, Ichigaku; Satake, Akiko; Onouchi, Hitoshi; Naito, Satoshi
2014-01-01
Expression of CGS1, which codes for an enzyme of methionine biosynthesis, is feedback-regulated by mRNA degradation in response to S-adenosyl-l-methionine (AdoMet). In vitro studies revealed that AdoMet induces translation arrest at Ser-94, upon which several ribosomes stack behind the arrested one, and mRNA degradation occurs at multiple sites that presumably correspond to individual ribosomes in a stacked array. Despite the significant contribution of stacked ribosomes to inducing mRNA degradation, little is known about the ribosomes in the stacked array. Here, we assigned the peptidyl-tRNA species of the stacked second and third ribosomes to their respective codons and showed that they are arranged at nine-codon intervals behind the Ser-94 codon, indicating tight stacking. Puromycin reacts with peptidyl-tRNA in the P-site, releasing the nascent peptide as peptidyl-puromycin. This reaction is used to monitor the activity of the peptidyltransferase center (PTC) in arrested ribosomes. Puromycin reaction of peptidyl-tRNA on the AdoMet-arrested ribosome, which is stalled at the pre-translocation step, was slow. This limited reactivity can be attributed to the peptidyl-tRNA occupying the A-site at this step rather than to suppression of PTC activity. In contrast, puromycin reactions of peptidyl-tRNA with the stacked second and third ribosomes were slow but were not as slow as pre-translocation step ribosomes. We propose that the anticodon end of peptidyl-tRNA resides in the A-site of the stacked ribosomes and that the stacked ribosomes are stalled at an early step of translocation, possibly at the P/E hybrid state. PMID:24652291
Lu, Zhengliang; Zhao, Yuanchao; Chen, Baolian; Huang, Ximing; Fan, Chunhua
2014-07-01
The title compound, [MnCl2(C24H20N6)], has been synthesized and characterized based on the multifunctional ligand 2,5-bis(2,2'-bipyridyl-6-yl)-3,4-diazahexa-2,4-diene (L). The Mn(II) centre is five-coordinate with an approximately square-pyramidal geometry. The L ligand acts as a tridendate chelating ligand. The mononuclear molecules are bridged into a one-dimensional chain by two C-H···Cl hydrogen bonds. These chains are assembled into a two-dimensional layer through π-π stacking interactions between adjacent uncoordinated bipyridyl groups. Furthermore, a three-dimensional supramolecular framework is attained through π-π stacking interactions between adjacent coordinated bipyridyl groups. PMID:24992119
De, Suvranu; Deo, Dhannanjay; Sankaranarayanan, Ganesh; Arikatla, Venkata S.
2012-01-01
Background While an update rate of 30 Hz is considered adequate for real time graphics, a much higher update rate of about 1 kHz is necessary for haptics. Physics-based modeling of deformable objects, especially when large nonlinear deformations and complex nonlinear material properties are involved, at these very high rates is one of the most challenging tasks in the development of real time simulation systems. While some specialized solutions exist, there is no general solution for arbitrary nonlinearities. Methods In this work we present PhyNNeSS - a Physics-driven Neural Networks-based Simulation System - to address this long-standing technical challenge. The first step is an off-line pre-computation step in which a database is generated by applying carefully prescribed displacements to each node of the finite element models of the deformable objects. In the next step, the data is condensed into a set of coefficients describing neurons of a Radial Basis Function network (RBFN). During real-time computation, these neural networks are used to reconstruct the deformation fields as well as the interaction forces. Results We present realistic simulation examples from interactive surgical simulation with real time force feedback. As an example, we have developed a deformable human stomach model and a Penrose-drain model used in the Fundamentals of Laparoscopic Surgery (FLS) training tool box. Conclusions A unique computational modeling system has been developed that is capable of simulating the response of nonlinear deformable objects in real time. The method distinguishes itself from previous efforts in that a systematic physics-based pre-computational step allows training of neural networks which may be used in real time simulations. We show, through careful error analysis, that the scheme is scalable, with the accuracy being controlled by the number of neurons used in the simulation. PhyNNeSS has been integrated into SoFMIS (Software Framework for Multimodal
De, Suvranu; Deo, Dhannanjay; Sankaranarayanan, Ganesh; Arikatla, Venkata S
2011-08-01
BACKGROUND: While an update rate of 30 Hz is considered adequate for real time graphics, a much higher update rate of about 1 kHz is necessary for haptics. Physics-based modeling of deformable objects, especially when large nonlinear deformations and complex nonlinear material properties are involved, at these very high rates is one of the most challenging tasks in the development of real time simulation systems. While some specialized solutions exist, there is no general solution for arbitrary nonlinearities. METHODS: In this work we present PhyNNeSS - a Physics-driven Neural Networks-based Simulation System - to address this long-standing technical challenge. The first step is an off-line pre-computation step in which a database is generated by applying carefully prescribed displacements to each node of the finite element models of the deformable objects. In the next step, the data is condensed into a set of coefficients describing neurons of a Radial Basis Function network (RBFN). During real-time computation, these neural networks are used to reconstruct the deformation fields as well as the interaction forces. RESULTS: We present realistic simulation examples from interactive surgical simulation with real time force feedback. As an example, we have developed a deformable human stomach model and a Penrose-drain model used in the Fundamentals of Laparoscopic Surgery (FLS) training tool box. CONCLUSIONS: A unique computational modeling system has been developed that is capable of simulating the response of nonlinear deformable objects in real time. The method distinguishes itself from previous efforts in that a systematic physics-based pre-computational step allows training of neural networks which may be used in real time simulations. We show, through careful error analysis, that the scheme is scalable, with the accuracy being controlled by the number of neurons used in the simulation. PhyNNeSS has been integrated into SoFMIS (Software Framework for Multimodal
Shahmansouri, M.; Mamun, A. A.
2014-03-15
Linear and nonlinear propagation of dust-acoustic waves in a magnetized strongly coupled dusty plasma is theoretically investigated. The normal mode analysis (reductive perturbation method) is employed to investigate the role of ambient/external magnetic field, obliqueness, and effective electrostatic dust-temperature in modifying the properties of linear (nonlinear) dust-acoustic waves propagating in such a strongly coupled dusty plasma. The effective electrostatic dust-temperature, which arises from strong electrostatic interactions among highly charged dust, is considered as a dynamical variable. The linear dispersion relation (describing the linear propagation characteristics) for the obliquely propagating dust-acoustic waves is derived and analyzed. On the other hand, the Korteweg-de Vries equation describing the nonlinear propagation of the dust-acoustic waves (particularly, propagation of dust-acoustic solitary waves) is derived and solved. It is shown that the combined effects of obliqueness, magnitude of the ambient/external magnetic field, and effective electrostatic dust-temperature significantly modify the basic properties of linear and nonlinear dust-acoustic waves. The results of this work are compared with those observed by some laboratory experiments.
Extremely strong tubular stacking of aromatic oligoamide macrocycles
Kline, Mark A.; Wei, Xiaoxi; Horner, Ian J.; Liu, Rui; Chen, Shuang; Chen, Si; Yung, Ka Yi; Yamato, Kazuhiro; Cai, Zhonghou; Bright, Frank V.; Zeng, Xiao Cheng; Gong, Bing
2015-01-01
As the third-generation rigid macrocycles evolved from progenitor 1, cyclic aromatic oligoamides 3, with a backbone of reduced constraint, exhibit extremely strong stacking with an astoundingly high affinity (estimated lower limit of K_{dimer} > 10^{13} M^{-1} in CHCl_{3}), which leads to dispersed tubular stacks that undergo further assembly in solution. Computational study reveals a very large binding energy (-49.77 kcal mol^{-1}) and indicates highly cooperative local dipole interactions that account for the observed strength and directionality for the stacking of 3. In the solid-state, X-ray diffraction (XRD) confirms that the aggregation of 3 results in well-aligned tubular stacks. The persistent tubular assemblies of 3, with their non-deformable sub-nm pore, are expected to possess many interesting functions. One such function, transmembrane ion transport, is observed for 3.
Extremely strong tubular stacking of aromatic oligoamide macrocycles
Kline, Mark A.; Wei, Xiaoxi; Horner, Ian J.; Liu, Rui; Chen, Shuang; Chen, Si; Yung, Ka Yi; Yamato, Kazuhiro; Cai, Zhonghou; Bright, Frank V.; Zeng, Xiao Cheng; Gong, Bing
2014-09-16
As the third-generation rigid macrocycles evolved from progenitor 1, cyclic aromatic oligoamides 3, with a backbone of reduced constraint, exhibit extremely strong stacking with an astoundingly high affinity (estimated lower limit of K-_{dimer} > 10^{13} M^{-1} in CHCl_{3}), which leads to dispersed tubular stacks that undergo further assembly in solution. Computational study reveals a very large binding energy (-49.77 kcal mol^{-1}) and indicates highly cooperative local dipole interactions that account for the observed strength and directionality for the stacking of 3. In the solid-state, X-ray diffraction (XRD) confirms that the aggregation of 3 results in well-aligned tubular stacks. Furthermore, the persistent tubular assemblies of 3, with their non-deformable sub-nm pore, are expected to possess many interesting functions. One such function, transmembrane ion transport, is observed for 3.
Extremely strong tubular stacking of aromatic oligoamide macrocycles
Kline, Mark A.; Wei, Xiaoxi; Horner, Ian J.; Liu, Rui; Chen, Shuang; Chen, Si; Yung, Ka Yi; Yamato, Kazuhiro; Cai, Zhonghou; Bright, Frank V.; et al
2014-09-16
As the third-generation rigid macrocycles evolved from progenitor 1, cyclic aromatic oligoamides 3, with a backbone of reduced constraint, exhibit extremely strong stacking with an astoundingly high affinity (estimated lower limit of K-dimer > 1013 M-1 in CHCl3), which leads to dispersed tubular stacks that undergo further assembly in solution. Computational study reveals a very large binding energy (-49.77 kcal mol-1) and indicates highly cooperative local dipole interactions that account for the observed strength and directionality for the stacking of 3. In the solid-state, X-ray diffraction (XRD) confirms that the aggregation of 3 results in well-aligned tubular stacks. Furthermore, themore » persistent tubular assemblies of 3, with their non-deformable sub-nm pore, are expected to possess many interesting functions. One such function, transmembrane ion transport, is observed for 3.« less
Extremely strong tubular stacking of aromatic oligoamide macrocycles
Kline, Mark A.; Wei, Xiaoxi; Horner, Ian J.; Liu, Rui; Chen, Shuang; Chen, Si; Yung, Ka Yi; Yamato, Kazuhiro; Cai, Zhonghou; Bright, Frank V.; et al
2015-01-01
As the third-generation rigid macrocycles evolved from progenitor 1, cyclic aromatic oligoamides 3, with a backbone of reduced constraint, exhibit extremely strong stacking with an astoundingly high affinity (estimated lower limit of Kdimer > 1013 M-1 in CHCl3), which leads to dispersed tubular stacks that undergo further assembly in solution. Computational study reveals a very large binding energy (-49.77 kcal mol-1) and indicates highly cooperative local dipole interactions that account for the observed strength and directionality for the stacking of 3. In the solid-state, X-ray diffraction (XRD) confirms that the aggregation of 3 results in well-aligned tubular stacks. The persistentmore » tubular assemblies of 3, with their non-deformable sub-nm pore, are expected to possess many interesting functions. One such function, transmembrane ion transport, is observed for 3.« less
Mechanical Stiffening of Porphyrin Nanorings through Supramolecular Columnar Stacking
2013-01-01
Solvent-induced aggregates of nanoring cyclic polymers may be transferred by electrospray deposition to a surface where they adsorb as three-dimensional columnar stacks. The observed stack height varies from single rings to four stacked rings with a layer spacing of 0.32 ± 0.04 nm as measured using scanning tunneling microscopy. The flexibility of the nanorings results in distortions from a circular shape, and we show, through a comparison with Monte Carlo simulations, that the bending stiffness increases linearly with the stack height. Our results show that noncovalent interactions may be used to control the shape and mechanical properties of artificial macromolecular aggregates offering a new route to solvent-induced control of two-dimensional supramolecular organization. PMID:23789845
Chen, X.; Heidbrink, W. W.; Kramer, G. J.; Nazikian, R.; Grierson, B. A.; Podesta, M.; Van Zeeland, M. A.; Pace, D. C.; Petty, C. C.; Fisher, R. K.; Zeng, L.; Austin, M. E.
2014-08-15
Two key insights into interactions between Alfvén eigenmodes (AEs) and energetic particles in the plasma core are gained from measurements and modeling of first-orbit beam-ion loss in DIII-D. First, the neutral beam-ion first-orbit losses are enhanced by AEs and a single AE can cause large fast-ion displacement. The coherent losses are from born trapped full energy beam-ions being non-resonantly scattered by AEs onto loss orbits within their first poloidal transit. The loss amplitudes scale linearly with the mode amplitude but the slope is different for different modes. The radial displacement of fast-ions by individual AEs can be directly inferred from the measurements. Second, oscillations in the beam-ion first-orbit losses are observed at the sum, difference, and harmonic frequencies of two independent AEs. These oscillations are not plasma modes and are absent in magnetic, density, and temperature fluctuations. The origin of the non-linearity as a wave-particle coupling is confirmed through bi-coherence analysis, which is clearly observed because the coherences are preserved by the first-orbit loss mechanism. An analytic model and full orbit simulations show that the non-linear features seen in the loss signal can be explained by a non-linear interaction between the fast ions and the two independent AEs.
Two-oscillator model of trapped-modes interaction in a nonlinear bilayer fish-scale metamaterial
NASA Astrophysics Data System (ADS)
Tuz, Vladimir R.; Kochetov, Bogdan A.; Kochetova, Lyudmila A.; Mladyonov, Pavel L.; Prosvirnin, Sergey L.
2015-02-01
We discuss a similarity between resonant oscillations in two nonlinear systems; namely, a chain of coupled Duffing oscillators and a bilayer fish-scale metamaterial. In such systems two different resonant states arise which differ in their spectral lines. The spectral line of the first resonant state has a Lorentzian form, whereas the second one has a Fano form. This difference leads to a specific nonlinear response of the systems which manifests itself in the appearance of closed loops in spectral lines and bending and overlapping of resonant curves. Conditions for achieving bistability and multistability are determined.
Full Piezoelectric Multilayer-Stacked Hybrid Actuation/Transduction Systems
NASA Technical Reports Server (NTRS)
Su, Ji; Jiang, Xiaoning; Zu, Tian-Bing
2011-01-01
The Stacked HYBATS (Hybrid Actuation/Transduction system) demonstrates significantly enhanced electromechanical performance by using the cooperative contributions of the electromechanical responses of multilayer, stacked negative strain components and positive strain components. Both experimental and theoretical studies indicate that, for Stacked HYBATS, the displacement is over three times that of a same-sized conventional flextensional actuator/transducer. The coupled resonance mode between positive strain and negative strain components of Stacked HYBATS is much stronger than the resonance of a single element actuation only when the effective lengths of the two kinds of elements match each other. Compared with the previously invented hybrid actuation system (HYBAS), the multilayer Stacked HYBATS can be designed to provide high mechanical load capability, low voltage driving, and a highly effective piezoelectric constant. The negative strain component will contract, and the positive strain component will expand in the length directions when an electric field is applied on the device. The interaction between the two elements makes an enhanced motion along the Z direction for Stacked-HYBATS. In order to dominate the dynamic length of Stacked-HYBATS by the negative strain component, the area of the cross-section for the negative strain component will be much larger than the total cross-section areas of the two positive strain components. The transverse strain is negative and longitudinal strain positive in inorganic materials, such as ceramics/single crystals. Different piezoelectric multilayer stack configurations can make a piezoelectric ceramic/single-crystal multilayer stack exhibit negative strain or positive strain at a certain direction without increasing the applied voltage. The difference of this innovation from the HYBAS is that all the elements can be made from one-of-a-kind materials. Stacked HYBATS can provide an extremely effective piezoelectric
Lateral excitonic switching in vertically stacked quantum dots
NASA Astrophysics Data System (ADS)
Jarzynka, Jarosław R.; McDonald, Peter G.; Shumway, John; Galbraith, Ian
2016-06-01
We show that the application of a vertical electric field to the Coulomb interacting system in stacked quantum dots leads to a 90° in-plane switching of charge probability distribution in contrast to a single dot, where no such switching exists. Results are obtained using path integral quantum Monte Carlo with realistic dot geometry, alloy composition, and piezo-electric potential profiles. The origin of the switching lies in the strain interactions between the stacked dots hence the need for more than one layer of dots. The lateral polarization and electric field dependence of the radiative lifetimes of the excitonic switch are also discussed.
49 CFR 178.1055 - Stacking test.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 49 Transportation 3 2013-10-01 2013-10-01 false Stacking test. 178.1055 Section 178.1055... Containers § 178.1055 Stacking test. (a) General. The stacking test must be conducted for the qualification of all Flexible Bulk Containers design types. (b) Special preparation for the stacking test....
NASA Astrophysics Data System (ADS)
Sun, Wen-Rong; Tian, Bo; Wang, Yu-Feng; Zhen, Hui-Ling
2015-06-01
Three-coupled fourth-order nonlinear Schrödinger equations describe the dynamics of alpha helical proteins with the interspine coupling at the higher order. Through symbolic computation and binary Bell-polynomial approach, bilinear forms and N-soliton solutions for such equations are constructed. Key point lies in the introduction of auxiliary functions in the Bell-polynomial expression. Asymptotic analysis is applied to investigate the elastic interaction between the two solitons: two solitons keep their original amplitudes, energies and velocities invariant after the interaction except for the phase shifts. Soliton amplitudes are related to the energy distributed in the solitons of the three spines. Overtaking interaction, head-on interaction and bound-state solitons of two solitons are given. Bound states of three bright solitons arise when all of them propagate in parallel. Elastic interaction between the bound-state solitons and one bright soliton is shown. Increase of the lattice parameter can lead to the increase of the soliton velocity, that is, the interaction period becomes shorter. The solitons propagating along the neighbouring spines are found to interact elastically. Those solitons, exhibited in this paper, might be viewed as a possible carrier of bio-energy transport in the protein molecules.
Fuel cell stack compressive loading system
Fahle, Ronald W.; Reiser, Carl A.
1982-01-01
A fuel cell module comprising a stack of fuel cells with reactant gas manifolds sealed against the external surfaces of the stack includes a constraint system for providing a compressive load on the stack wherein the constraint system maintains the stack at a constant height (after thermal expansion) and allows the compressive load to decrease with time as a result of the creep characteristics of the stack. Relative motion between the manifold sealing edges and the stack surface is virtually eliminated by this constraint system; however it can only be used with a stack having considerable resiliency and appropriate thermal expansion and creep characteristics.
Li, Chenrui; Wang, Qian; Ren, Tianjing; Zhang, Yufeng; Lam, Christopher Wai Kei; Chow, Moses S S; Zuo, Zhong
2016-09-01
Piperine (PIP), the major alkaloid component from Piper longum L. and Piper nigrum L., could enhance the bioavailabilities of other drugs including rosuvastatin, peurarin and docetaxel (DOX) via inhibition of CYP3A and P-glycoprotein activity. Nevertheless, the effect of such drug combination usage on the in vivo exposure of PIP has not been investigated due to lack of assay for the simultaneous determination of PIP and other drugs such as DOX. Besides, the reported pharmacokinetics of PIP varied a lot without appropriate bioavailability determined from the same dose. In the current study, an LC/MS/MS method has been developed to simultaneously determine the plasma concentrations of PIP and DOX and further applied to investigate the pharmacokinetics properties of PIP after oral and intravenous administrations as well as the pharmacokinetics interactions between PIP and DOX after their co-administration. A simple protein precipitation method was employed for plasma sample treatment by adding a mixture of methanol and acetonitrile (1:1, v/v) with glibenclamide as internal standard (IS). The LC/MS/MS system consisted of Agilent 6430 series LC pumps and auto-sampler. The chromatographic separation was carried out in 15min on a Waters C18 column (150×3.9mm i.d., 4μm) with a mobile phase containing 0.2% formic acid and acetonitrile (1:1, v/v) at a flow rate of 0.4ml/min. The detection was performed using the positive ion electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode with precursor-to-product ion transitions at m/z 286.1→201.1 for PIP, m/z 830.3→548.9 for DOX and m/z 494.2→369.0 for IS. The method demonstrated good linearity for both PIP and DOX over the concentration range of 2.5-1280ng/ml with LLOD at 2.5ng/ml. The intra-day and inter-day precisions were less than 13.34% and relative error (R.E.) representing accuracy was in the range of -11.38 to 3.15%. The recoveries of PIP, DOX and IS were above 75% and there was no matrix effect
Slippage in stacking of graphene nanofragments induced by spin polarization
NASA Astrophysics Data System (ADS)
Lei, Yanyu; Jiang, Wanrun; Dai, Xing; Song, Ruixia; Wang, Bo; Gao, Yang; Wang, Zhigang
2015-06-01
Spin polarization and stacking are interesting effects in complex molecular systems and are both presented in graphene-based materials. Their possible combination may provide a new perspective in understanding the intermolecular force. The nanoscale graphene structures with zigzag edges could possess spin-polarized ground states. However, the mechanical effect of spin polarization in stacking of graphene nanofragments is not clear. Here we demonstrate the displacement between two stacked rhombic graphene nanofragments induced by spin polarization, using first-principles density-functional methods. We found that, in stacking of two rhombic graphene nanofragments, a spin-polarized stacked conformation with zero total spin is energetically more favorable than the closed-shell stacking. The spin-polarized conformation gives a further horizontal interlayer displacement within 1 angstrom compared with the closed-shell structure. This result highlights that, besides the well-known phenomenologically interpreted van der Waals forces, a specific mechanism dependent on the monomeric spin polarization may lead to obvious mechanical effects in some intermolecular interactions.
Slippage in stacking of graphene nanofragments induced by spin polarization.
Lei, Yanyu; Jiang, Wanrun; Dai, Xing; Song, Ruixia; Wang, Bo; Gao, Yang; Wang, Zhigang
2015-01-01
Spin polarization and stacking are interesting effects in complex molecular systems and are both presented in graphene-based materials. Their possible combination may provide a new perspective in understanding the intermolecular force. The nanoscale graphene structures with zigzag edges could possess spin-polarized ground states. However, the mechanical effect of spin polarization in stacking of graphene nanofragments is not clear. Here we demonstrate the displacement between two stacked rhombic graphene nanofragments induced by spin polarization, using first-principles density-functional methods. We found that, in stacking of two rhombic graphene nanofragments, a spin-polarized stacked conformation with zero total spin is energetically more favorable than the closed-shell stacking. The spin-polarized conformation gives a further horizontal interlayer displacement within 1 angstrom compared with the closed-shell structure. This result highlights that, besides the well-known phenomenologically interpreted van der Waals forces, a specific mechanism dependent on the monomeric spin polarization may lead to obvious mechanical effects in some intermolecular interactions. PMID:26078005
Single-molecule dissection of stacking forces in DNA.
Kilchherr, Fabian; Wachauf, Christian; Pelz, Benjamin; Rief, Matthias; Zacharias, Martin; Dietz, Hendrik
2016-09-01
We directly measured at the single-molecule level the forces and lifetimes of DNA base-pair stacking interactions for all stack sequence combinations. Our experimental approach combined dual-beam optical tweezers with DNA origami components to allow positioning of blunt-end DNA helices so that the weak stacking force could be isolated. Base-pair stack arrays that lacked a covalent backbone connection spontaneously dissociated at average rates ranging from 0.02 to 500 per second, depending on the sequence combination and stack array size. Forces in the range from 2 to 8 piconewtons that act along the helical direction only mildly accelerated the stochastic unstacking process. The free-energy increments per stack that we estimate from the measured forward and backward kinetic rates ranged from -0.8 to -3.4 kilocalories per mole, depending on the sequence combination. Our data contributes to understanding the mechanics of DNA processing in biology, and it is helpful for designing the kinetics of DNA-based nanoscale devices according to user specifications. PMID:27609897
NASA Technical Reports Server (NTRS)
Bell, T. F.
1984-01-01
A theory is presented of the nonlinear gyroresonance interaction that takes place in the magnetosphere between energetic electrons and coherent VLF waves propagating in the whistler mode at an arbitrary angle psi with respect to the earth's magnetic field B-sub-0. Particularly examined is the phase trapping (PT) mechanism believed to be responsible for the generation of VLF emissions. It is concluded that near the magnetic equatorial plane gradients of psi may play a very important part in the PT process for nonducted waves. Predictions of a higher threshold value for PT for nonducted waves generally agree with experimental data concerning VLF emission triggering by nonducted waves.
Split stack blowout prevention system
Crager, B.L.; Ray, D.R.; Steddum, R.E.
1980-03-18
A blowout prevention system for an offshore structure positioned on the underwater bottom in a body of water which contains moving ice masses that could force the structure off location wherein a surface blowout preventer stack for conventional well control is connected to the upper end of a riser with the lower end of the riser being disconnectably connected to a subsurface blowout preventer stack which provides the necessary well control should the structure be forced off location. The subsurface stack is positioned on a wellhead located in a chamber in the subsea bottom and is disconnectably connected to the riser so that the riser may be quickly removed from the subsea bottom should the structure be forced off location.
Du Chaohai; Liu Pukun
2010-03-15
The stability of the millimeter-wave gyrotron-traveling-wave-tube (gyro-TWT) amplifier can be effectively improved via controlling the propagation characteristics of the operating modes using lossy dielectric-lined (DL) waveguide. Self-consistent nonlinear theory of the electron cyclotron maser (ECM) interaction in lossy DL circuit is developed based on a full-wave study of the propagation characteristics of the DL waveguide. This nonlinear theory fully takes into consideration the waveguide structure and the lossy dielectric characteristics. It is capable of accurately calculating the ECM instability between a cyclotron harmonic and a circular polarized mode, and effectively predicting the nonlinear stability of the DL waveguide-based gyro-TWT. Systematic investigation of a Ka-band TE{sub 01} mode DL waveguide-based gyro-TWT is carried out, and numerical calculation reveals a series of interesting results. This work provides a basic theoretical tool for further exploring the application of the lossy DL waveguide in millimeter-wave gyro-TWTs.
NASA Astrophysics Data System (ADS)
Sota, Shigetoshi; Tohyama, Takami; Brazovskii, Serguei
2012-02-01
The optical response of organic compounds has been attracting much attention. The one of the reasons is the huge non-linear and ultrafast optical response [K. Yamamoto et. al., J. Phys. Soc. Jpn. 77, 074709(2008)]. In order to investigate such optical properties, we carry out dynamical DMRG calculations to obtain optical responses in the 1/4-filled one-dimensional Hubbard model including the nearest neighbor Coulomb interaction and the alternating electron hopping. The charge gap [S. Nishimoto, M. Takahashi, and Y. Ohta, J. Phys. Soc. Jpn. 69, 1594(2000)] and the bound state [H. Benthien and E. Jeckelmann, Eur. Phys. J. B 44, 287(2005)] in this model have been discussed based on DMRG calculations. In the present study, we introduce an alternating on-site potential giving the polarization in the system into the dimerized Hubbard model, which breaks the reflection symmetry of the system. In this talk, we discuss the obtained linear and the 2nd order non-linear optical susceptibility in order to make a prediction for non-linear optical experiments in the future.
NASA Astrophysics Data System (ADS)
Latifi, A.
2016-07-01
A special case of coupled integrable nonlinear equations with a singular dispersion law is derived in the context of the small amplitude limit of general wave equations in a fluid-type warm electrons/cold ions plasma irradiated by a continuous laser beam. This model accounts for a nonlinear mode coupling of the electrostatic wave with the ion sound wave and is shown to be highly unstable. Its instability is understood as a continuous secular transfer of energy from the electrostatic wave to the ion sound wave through the ponderomotive force. The exact asymptotic solution of the system is constructed and shows that the dynamics of the energy transfer results in a singular asymptotic behavior of the ion sound wave, which explains the low penetration of the incident laser beam.
Nonlinear optics at interfaces
Chen, C.K.
1980-12-01
Two aspects of surface nonlinear optics are explored in this thesis. The first part is a theoretical and experimental study of nonlinear intraction of surface plasmons and bulk photons at metal-dielectric interfaces. The second part is a demonstration and study of surface enhanced second harmonic generation at rough metal surfaces. A general formulation for nonlinear interaction of surface plasmons at metal-dielectric interfaces is presented and applied to both second and third order nonlinear processes. Experimental results for coherent second and third harmonic generation by surface plasmons and surface coherent antiStokes Raman spectroscopy (CARS) are shown to be in good agreement with the theory.
Pressurized electrolysis stack with thermal expansion capability
Bourgeois, Richard Scott
2015-07-14
The present techniques provide systems and methods for mounting an electrolyzer stack in an outer shell so as to allow for differential thermal expansion of the electrolyzer stack and shell. Generally, an electrolyzer stack may be formed from a material with a high coefficient of thermal expansion, while the shell may be formed from a material having a lower coefficient of thermal expansion. The differences between the coefficients of thermal expansion may lead to damage to the electrolyzer stack as the shell may restrain the thermal expansion of the electrolyzer stack. To allow for the differences in thermal expansion, the electrolyzer stack may be mounted within the shell leaving a space between the electrolyzer stack and shell. The space between the electrolyzer stack and the shell may be filled with a non-conductive fluid to further equalize pressure inside and outside of the electrolyzer stack.
NASA Astrophysics Data System (ADS)
Manfredi, Sabato
2016-06-01
Large-scale dynamic systems are becoming highly pervasive in their occurrence with applications ranging from system biology, environment monitoring, sensor networks, and power systems. They are characterised by high dimensionality, complexity, and uncertainty in the node dynamic/interactions that require more and more computational demanding methods for their analysis and control design, as well as the network size and node system/interaction complexity increase. Therefore, it is a challenging problem to find scalable computational method for distributed control design of large-scale networks. In this paper, we investigate the robust distributed stabilisation problem of large-scale nonlinear multi-agent systems (briefly MASs) composed of non-identical (heterogeneous) linear dynamical systems coupled by uncertain nonlinear time-varying interconnections. By employing Lyapunov stability theory and linear matrix inequality (LMI) technique, new conditions are given for the distributed control design of large-scale MASs that can be easily solved by the toolbox of MATLAB. The stabilisability of each node dynamic is a sufficient assumption to design a global stabilising distributed control. The proposed approach improves some of the existing LMI-based results on MAS by both overcoming their computational limits and extending the applicative scenario to large-scale nonlinear heterogeneous MASs. Additionally, the proposed LMI conditions are further reduced in terms of computational requirement in the case of weakly heterogeneous MASs, which is a common scenario in real application where the network nodes and links are affected by parameter uncertainties. One of the main advantages of the proposed approach is to allow to move from a centralised towards a distributed computing architecture so that the expensive computation workload spent to solve LMIs may be shared among processors located at the networked nodes, thus increasing the scalability of the approach than the network