Resonance Overlap Research Articles

Greatly Enhanced Merger Rates of Compact-object Binaries in Non-spherical Nuclear Star Clusters

Abstract The Milky Way and a significant fraction of galaxies are observed to host a central massive black hole (MBH) embedded in a non-spherical nuclear star cluster. We study the secular orbital evolution of compact-object binaries in these environments and characterize the excitation of extremely large eccentricities that can lead to mergers by gravitational radiation. We find that the eccentricity excitation occurs most efficiently when the nodal precession timescale of the binary’s orbit around the MBH due to the non-spherical cluster becomes comparable (within a factor of ∼10) to the timescale on which the binary is torqued by the MBH due to the Lidov–Kozai (LK) mechanism. We show that in this regime the perturbations due to the cluster increase the fraction of systems that reach extreme eccentricities ( ) by a factor of ∼10–100 compared to the idealized case of a spherical cluster, increasing the merger rates of compact objects by a similar factor. We identify two main channels that lead to this extreme eccentricity excitation: (i) chaotic diffusion of the eccentricities due to resonance overlap; (ii) cluster-driven variations of the mutual inclinations between the binary orbit and its center-of-mass orbit around the MBH, which can intensify the LK oscillations. We estimate that our mechanism can produce BH–BH and BH–neutron star binary merger rates of up to and , respectively. Thus, we propose the cluster-enhanced LK mechanism as a new channel for the merger of compact-object binaries, competing with scenarios that invoke isolated binary evolution or dynamical formation in globular clusters.

Solid‐State NMR H–N–(C)–H and H–N–C–C 3D/4D Correlation Experiments for Resonance Assignment of Large Proteins

Solid-state NMR spectroscopy can provide insight into protein structure and dynamics at the atomic level without inherent protein size limitations. However, a major hurdle to studying large proteins by solid-state NMR spectroscopy is related to spectral complexity and resonance overlap, which increase with molecular weight and severely hamper the assignment process. Here the use of two sets of experiments is shown to expand the tool kit of 1 H-detected assignment approaches, which correlate a given amide pair either to the two adjacent CO-CA pairs (4D hCOCANH/hCOCAcoNH), or to the amide 1 H of the neighboring residue (3D HcocaNH/HcacoNH, which can be extended to 5D). The experiments are based on efficient coherence transfers between backbone atoms using INEPT transfers between carbons and cross-polarization for heteronuclear transfers. The utility of these experiments is exemplified with application to assemblies of deuterated, fully amide-protonated proteins from approximately 20 to 60 kDa monomer, at magic-angle spinning (MAS) frequencies from approximately 40 to 55 kHz. These experiments will also be applicable to protonated proteins at higher MAS frequencies. The resonance assignment of a domain within the 50.4 kDa bacteriophage T5 tube protein pb6 is reported, and this is compared to NMR assignments of the isolated domain in solution. This comparison reveals contacts of this domain to the core of the polymeric tail tube assembly.

Ultracompact On-Chip Multiplexed Sensor Array Based on Dense Integration of Flexible 1-D Photonic Crystal Nanobeam Cavity With Large Free Spectral Range and High Q-Factor

A method for the dense integration of one-dimensional (1-D) photonic crystal nanobeam cavity (PCNC) based integrated sensor array (1-D-PCNC-ISA) is proposed. The 1-D-PCNC-ISA consists of multiple parallel-connected sensing channels with airgap separations. On each channel, only a single flexible 1-D-PCNC sensor with large free spectral range (FSR) and high Q-factor is contained. With proper engineering of the FSR, multiple ultracompact high-sensitivity 1-D-PCNC sensors can be integrated into microarrays without resonance overlap, and be interrogated simultaneously between a single input/output ports. Using 3-D finite-difference-time-domain (3-D-FDTD) method, the performance of the device is investigated theoretically in the whole paper. With optimization design, a large FSR as wide as 197 nm and high Q-factor 2 x 10 5 can be achieved. Moreover, the refractive index sensitivities of a 5-channel 1-D-PCNC-ISA as high as 170.6, 152.7, 138.5, 128.1, and 120.5 nm/RIU are obtained. Particularly, the footprint of a 5-channel 1-D-PCNC-ISA is ~7μm x 65μm (width by length), which is decreased by three orders of magnitude compared to the sensor arrays based on 2-D-PC cavity platforms. To the best of our knowledge, this is for the first time that a 1-D-PCNC based multichannel parallel-connected sensor array has been displayed with channel spacing as small as 0.195μm, extinction ratio > 20 dB and Q-factor > 10 5 , respectively, without using particular materials or complexities in fabrication. Both the specific result and the general idea are promising in future ultracompact lab-on-a-chip applications and nanophotonic integrations.

Probing Transient Release of Membrane-Sequestered Tyrosine-Based Signaling Motif by Solution NMR Spectroscopy.

Membrane sequestration of tyrosine-based signaling motifs of antigen receptors effectively restricts the signaling activities in resting lymphocytes. However, low level of basal signaling in resting cells is required for lymphocyte survival and antigen responsiveness, of which the molecular mechanism remains obscure. Here we probe the transient release of the cytoplasmic domain of the membrane-bound IgG heavy chain (mIgG-tail) by hydrogen exchange NMR spectroscopy, illustrating a dynamic molecular basis for its basal signaling activity. To solve the severe resonance overlap problem in the 2D spectra of mIgG-tail, a non-uniformly sampled pseudo-4D hydrogen exchange NMR experiment has been exploited to quantitatively measure site-specific hydrogen exchange rates. Our solution NMR study reveals transient solvent exposure of the ITT signaling motif that can be further enhanced by calcium ion, and provides insight into the mechanism of lymphocyte basal signaling.

Coupling-based Huygens' meta-atom utilizing bilayer complementary plasmonic structure for light manipulation.

Huygens' meta-atom is the basic building unit of Huygens' metasurfaces allowing for almost arbitrary wavefront shaping across a surface. We here present a kind of Huygens' meta-atom by coupling a nanodisk to its Babinet-complementary structure (nanohole), and develop an optical lumped nanocircuit model to analyze vertical and lateral coupling effects and resonance frequencies. Simulation results show that the tuned coupling via lateral misalignment between the two nanostructures is sufficient to shape the wavefront without changing the dimensions or orientations of antennas. By tuning the coupling via lateral misalignment, we design a reflective gradient metasurface based on one coupled mode and a high-efficiency transmissive gradient metasurface working in the spectral overlap of electric and magnetic resonances to realize beam deflection. The proposed coupling-based Huygens' meta-atom is a new building block for plasmonic metasurfaces with enhanced light-matter interactions, high-efficiency and almost arbitrary wavefront shaping over the full electromagnetic spectrum.

Fano-type spectra and other interference effects in an all-dielectric nanoshell

Large spectral variations in the extinction of nanostructures are important for many applications like optical antennas, cloaking materials, optical circuits and others. Such features in extinction spectra are typically attained using plasmonic particles and high-index or complex nanostructures. In this work, we show that large interference structures can manifest even in the extinction spectra of a single dielectric particle with a low relative refractive index (), and notably even as a spectral region of transparency and directional scattering of incident light. This is observed when the core and shell resonances of a layered spherical particle have overlaps with each other in the energy spectrum. Interference between the core and shell modes results in larger spectral features in magnitudes of the scattering constants an, bn i.e. a strong enhancement of what is traditionally called the ripple structure in the extinction spectra of a dielectric particle. This effect is in addition to any possible overlap of electric resonances of two different mode numbers or the overlap of an electric and magnetic resonance, which have been shown to result in sharp asymmetric (Fano) resonances in the forward or backscattering spectra of a high-index or metallic particle.

Polarization independent high transmission large numerical aperture laser beam focusing and deflection by dielectric Huygens’ metasurfaces

In this letter, we propose all-dielectric Huygens’ metasurface structures to construct high numerical aperture flat lenses and beam deflecting devices. The designed metasurface consists of two-dimensional array of all-dielectric nanodisk resonators with spatially varying radii, thereby introducing judiciously designed phase shift to the propagating light. Owing to the overlap of Mie-type magnetic and electric resonances, high transmission was achieved with rigorous design analysis. The designed flat lenses have numerical aperture value of 0.85 and transmission values around 80%. It also offers easy fabrication and compatibility with available semiconductor technology. This spectrally and physically scalable, versatile design could implement efficient wavefront manipulation or beam shaping for high power laser beams, as well as various optical microscopy applications without requiring plasmonic structures that are susceptible to ohmic loss of metals and sensitive to the polarization of light.

The dynamical evolution and the force model for asteroid (196256) 2003 EH1

This paper is devoted to the dynamics of asteroid (196256) 2003 EH1 which belongs to the Amor group. It is known that asteroid 2003 EH1 is associated with one of the main annual meteor showers – the Quadrantids. In this work we analyze the influence of various perturbing factors on the asteroid motion. The perturbations’ estimation was done by five different methods based on the nominal orbit evolution and the size of the initial confidence region. The most significant influences on the dynamical evolution of 2003 EH1 are gravitational forces from the Sun, major planets and the Moon, and the relativistic effects (RE) of the Sun. The Earth, the Sun and Jupiter oblateness; gravitational perturbations from Pallas, Ceres, Vesta and Pluto; and the RE of planets, the Moon, and Pluto are of less importance.The researches of chaoticity and evolution of asteroid 2003 EH1 were examined by integrating its motion equations along with 500 clones. The time interval (1000–4000 years) has been determined by integration precision estimation. We estimated the mean exponential growth factor of nearby orbits (MEGNO) and found that MEGNO < 2 only in the interval from 1700 year to 2300 year. After 2300 year the MEGNO parameter increases that indicates motion instability. It shows that the orbit may be considered as regular on the time interval of ±300 years from now, and as chaotic outside this interval. We suppose that the reasons are the frequent close approaches of the asteroid with Jupiter and the overlap of apsidal-nodal resonances.

Broadband transmission loss in the audible regime with a 3D sonic crystals by use of resonance overlap

The acoustic properties of a three-dimensional sonic crystal made of square-rod rigid scatterers incorporating a periodic arrangement of quarter wavelength resonators are theoretically and experimentally reported in this work. The periodicity of the system produces Bragg band gaps that can be tuned in frequency by modifying the orientation of the square-rod scatterers with respect to the incident wave. In addition, the quarter wavelength resonators introduce resonant band gaps that can be tuned by coupling the neighbor resonators. Bragg and resonant band gaps can overlap allowing the wave propagation control inside the periodic resonant medium. In particular, we theoretically and experimentally show that this system can produce a broad frequency band gap exceeding two and a half octaves (from 590 Hz to 3220 Hz) with transmission lower than 3%. Finite element methods were used to calculate the dispersion relation of the locally resonant system. The visco-thermal losses were accounted for in the quarter wav...

Gap-plasmon of Fe3O4@Ag core-shell nanostructures for highly enhanced fluorescence detection of Rhodamine B

A novel gap-plasmon of Fe3O4@Ag core-shell nanoparticles for surface enhanced fluorescence detection of Rhodamine B (RB) was developed. Fe3O4@Ag core-shell nanostructures with Ag shell and Fe3O4 core were synthetized by self-assembled method with the assistance of 3-mercaptopropyl trimethoxy silane (MPTS). To study the RB fluorescence enhanced by gap-plasmon, the fluorescence properties of RB on the substrates with different nanogap densities were systematically investigated, and the results showed that the fluorescence intensity of RB on Fe3O4@Ag core-shell NPs substrate was much stronger than that on bare glass substrate, and the fluorescence intensity was further improved by using multilayer Fe3O4@Ag core-shell NPs substrate which had higher nanogap density. Different from the mechanism that is based on the maximum overlap of the surface plasmon resonance (SPR) band and emission band, the mechanism of the fluorescence enhancement in our work is based on the localized surface plasmon (LSP) and the gap plasmon near-field coupling with the Fe3O4@Ag core-shell NPs. Besides, the detection limit obtained was as low as 1×10-7 mol/L, and the Fe3O4@Ag core-shell NPs substrate had high selectivity for RB fluorophores. It was demonstrated that the Fe3O4@Ag core-shell NPs substrate had activity, good stability, and selectivity for fluorescence detection of RB. And the detection of RB by the surface plasmon enhanced fluorescence was more convenient and rapid than the traditional detection methods in previous works.

Solvent signal suppression for high-resolution MAS-DNP

Dynamic nuclear polarization (DNP) has become a powerful tool to substantially increase the sensitivity of high-field magic angle spinning (MAS) solid-state NMR experiments. The addition of dissolved hyperpolarizing agents usually results in the presence of solvent signals that can overlap and obscure those of interest from the analyte. Here, two methods are proposed to suppress DNP solvent signals: a Forced Echo Dephasing experiment (FEDex) and TRAnsfer of Populations in DOuble Resonance Echo Dephasing (TRAPDORED) NMR. These methods reintroduce a heteronuclear dipolar interaction that is specific to the solvent, thereby forcing a dephasing of recoupled solvent spins and leaving acquired NMR spectra free of associated resonance overlap with the analyte. The potency of these methods is demonstrated on sample types common to MAS-DNP experiments, namely a frozen solution (of l-proline) and a powdered solid (progesterone), both containing deuterated glycerol as a DNP solvent. The proposed methods are efficient, simple to implement, compatible with other NMR experiments, and extendable past spectral editing for just DNP solvents. The sensitivity gains from MAS-DNP in conjunction with FEDex or TRAPDORED then permits rapid and uninterrupted sample analysis.

Fast profiling of metabolite mixtures using chemometric analysis of a speeded-up 2D heteronuclear correlation NMR experiment

One-dimensional (1D) NMR spectra of mixtures of metabolites suffer from severe overlap of spectral resonances and hence recent research in NMR-based metabolomics focuses on using two-dimensional (2D) NMR experiments for metabolite fingerprinting.

Dynamics and habitability in circumstellar planetary systems of known binary stars

We present a survey on exoplanetary systems of binary stars with stellar separations less than 100 au. For a sample of 11 binaries that harbour detected circumstellar giant planets we investigate the frequency of systems with secular resonances (SR) affecting the habitable zone (HZ). Secular resonances are connected to dynamically unstable or chaotic regions by enforcing highly eccentric motion. We apply a semi-analytical method to determine the locations of linear SR, which is based on finding the apsidal precession frequencies of the massive bodies. For configurations where the giant planet is located exterior to the HZ we find that there is always a SR interior to its orbit, the exact location of the SR strongly depends on the system's architecture. In systems with the giant planet interior to the HZ no SR can occur in the Newtonian framework. Taking into account the general relativistic precession of the perihelion, which increases the precession frequencies, planets with $a < 0.1$ au can cause SR in the HZ. We find two cases where the SR is located inside the HZ, and some more where it is close to the HZ. Generally, giant planets interior to the HZ are more favourable than exterior planets to avoid SR in the HZ. Around the location of the SR weaker mean-motion resonances are excited, and resonance overlap is possible. Existing analytical models are not as accurate as the semi-analytical method in locating the SR and deviate by $\sim 0.1$ au or more.

SUPPRESSION OF ELECTRON THERMAL CONDUCTION IN THE HIGH β INTRACLUSTER MEDIUM OF GALAXY CLUSTERS

ABSTRACT Understanding the thermodynamic state of the hot intracluster medium (ICM) in a galaxy cluster requires knowledge of the plasma transport processes, especially thermal conduction. The basic physics of thermal conduction in plasmas with ICM-like conditions has yet to be elucidated, however. We use particle-in-cell simulations and analytic models to explore the dynamics of an ICM-like plasma (with small gyroradius, large mean free path, and strongly sub-dominant magnetic pressure) driven by the diffusive heat flux associated with thermal conduction. Linear theory reveals that whistler waves are driven unstable by electron heat flux, even when the heat flux is weak. The resonant interaction of electrons with these waves then plays a critical role in scattering electrons and suppressing the heat flux. In a 1D model where only whistler modes that are parallel to the magnetic field are captured, the only resonant electrons are moving in the opposite direction to the heat flux, and the electron heat flux suppression is small. In 2D or more, oblique whistler modes also resonate with electrons moving in the direction of the heat flux. The overlap of resonances leads to effective symmetrization of the electron distribution function and a strong suppression of heat flux. The results suggest that thermal conduction in the ICM might be strongly suppressed, possibly to negligible levels.

Localized surface plasmon resonance improved lasing performance of Ag nanoparticles/organic dye random laser

Random lasing threshold reduction and emission enhancement were reported from a suspension of Ag nanoparticles (NPs) in a laser dye doped polymer film. To evaluate the effect of the localized surface plasmon resonance (LSPR) of metal NPs on random lasing from lasing dye, we carry out a comparative study of the random lasing performance of the Ag NPs and SiO2 NPs scattered dye doped polymer films. Random lasing emission was obtained from Ag NPs and SiO2 NPs scattered dye doped polymer films. The threshold was dramatically reduced from 0.01 to 0.003 mJ/pulse as Ag NPs was used as scatters instead of SiO2 NPs. Theoretical simulation indicates that a large localized electric field is built near the Ag particle surface which enhances the absorption of excitation light. Furthermore, excellent overlap of the plasmonic resonance of Ag NPs with the absorption and photoluminescence spectrum of the dye molecules promotes more dye molecules excited simultaneously to the higher energy levels and leads to more effective random lasing performance.

Analytical investigation of an isomerization system using the resonance overlap criterion

Analytical investigation of an isomerization system using the resonance overlap criterion

Fast ion profile stiffness due to the resonance overlap of multiple Alfvén eigenmodes

Fast ion pressure profiles flattened by multiple Alfvén eigenmodes (AEs) are investigated for various neutral beam deposition powers in a multi-phase simulation, which is a combination of classical simulation and hybrid simulation for energetic particles interacting with a magnetohydrodynamic fluid. Monotonic degradation of fast ion confinement and fast ion profile stiffness is found with increasing beam deposition power. The confinement degradation and profile stiffness are caused by a sudden increase in fast ion transport flux brought about by AEs for fast ion pressure gradients above a critical value. The critical pressure gradient and the corresponding beam deposition power depend on the radial location. The fast ion pressure gradient stays moderately above the critical value, and the profiles of the fast ion pressure and fast ion transport flux spread radially outward from the inner region, where the beam is injected. It is found that the square root of the MHD fluctuation energy is proportional to the beam deposition power. Analysis of the time evolutions of the fast ion energy flux profiles reveals that intermittent avalanches take place with contributions from the multiple eigenmodes. Surface of section plots demonstrate that the resonance overlap of multiple eigenmodes accounts for the sudden increase in fast ion transport with increasing beam power. The critical gradient and critical beam power for the profile stiffness are substantially higher than the marginal stability threshold.

THE DYNAMICAL RELATIONSHIP BETWEEN THE BAR AND SPIRAL PATTERNS OF NGC 1365

ABSTRACT Theories that attempt to explain the dynamical relationship between bar and spiral patterns in galactic disks make different predictions about the radial profile of the pattern speed. These are tested for the H-alpha bar and spiral patterns of NGC 1365. The radial profile of the pattern speed is measured by fitting mathematical models that are based on the Tremaine–Weinberg method. The results show convincing evidence for the bar rotating at a faster rate than the spiral pattern, inconsistent with a global wave mode or a manifold. There is evidence for mode coupling of the bar and spiral patterns at the overlap of corotation and inner Lindblad resonances (ILRs), but the evidence is unreliable and inconsistent. The results are the most consistent with the bar and spiral patterns being dynamically distinct features. The pattern speed of the bar begins near an ILR and ends near the corotation resonance (CR). The radial profile of the pattern speed beyond the bar most closely resembles what is expected for coupled spiral modes and tidal interactions.

Full particle orbit effects in regular and stochastic magnetic fields

We present a numerical study of charged particle motion in a time-independent magnetic field in cylindrical geometry. The magnetic field model consists of an unperturbed reversed-shear (non-monotonic q-profile) helical part and a perturbation consisting of a superposition of modes. Contrary to most of the previous studies, the particle trajectories are computed by directly solving the full Lorentz force equations of motion in a six-dimensional phase space using a sixth-order, implicit, symplectic Gauss-Legendre method. The level of stochasticity in the particle orbits is diagnosed using averaged, effective Poincare sections. It is shown that when only one mode is present, the particle orbits can be stochastic even though the magnetic field line orbits are not stochastic (i.e., fully integrable). The lack of integrability of the particle orbits in this case is related to separatrix crossing and the breakdown of the global conservation of the magnetic moment. Some perturbation consisting of two modes creates resonance overlapping, leading to Hamiltonian chaos in magnetic field lines. Then, the particle orbits exhibit a nontrivial dynamics depending on their energy and pitch angle. It is shown that the regions where the particle motion is stochastic decrease as the energy increases. The non-monotonicity of the q-profile implies the existence of magnetic ITBs (internal transport barriers) which correspond to shearless flux surfaces located in the vicinity of the q-profile minimum. It is shown that depending on the energy, these magnetic ITBs might or might not confine particles. That is, magnetic ITBs act as an energy-dependent particle confinement filter. Magnetic field lines in reversed-shear configurations exhibit topological bifurcations (from homoclinic to heteroclinic) due to separatrix reconnection. We show that a similar but more complex scenario appears in the case of particle orbits that depend in a non-trivial way on the energy and pitch angle of the particles.

Broadband Transmission Loss Using the Overlap of Resonances in 3D Sonic Crystals

The acoustic properties of a three-dimensional sonic crystal made of square-rod rigid scatterers incorporating a periodic arrangement of quarter wavelength resonators are theoretically and experimentally reported in this work. The periodicity of the system produces Bragg band gaps that can be tuned in frequency by modifying the orientation of the square-rod scatterers with respect to the incident wave. In addition, the quarter wavelength resonators introduce resonant band gaps that can be tuned by coupling the neighbor resonators. Bragg and resonant band gaps can overlap allowing the wave propagation control inside the periodic resonant medium. In particular, we show theoretically and experimentally that this system can produce a broad frequency band gap exceeding two and a half octaves (from 590 Hz to 3220 Hz) with transmission lower than 3%. Finite element methods were used to calculate the dispersion relation of the locally resonant system. The visco-thermal losses were accounted for in the quarter wavelength resonators to simulate the wave propagation in the semi-infinite structures and to compare the numerical results with the experiments performed in an echo-free chamber. The simulations and the experimental results are in good agreement. This work motivates interesting applications of this system as acoustic audible filters.