Haut PDF Study on neutron scattering in light water

Study on neutron scattering in light water

Study on neutron scattering in light water

Neutron Physics Department, Centro Atomico Bariloche, Argentina Abstract. It is presented a method to produce covariance matrices of the light water total cross section from thermal scattering laws of the JEFF-3.1.1 nuclear data library and CAB model. The generalized least square method was used to fit the LEAPR module parameters of the processing tool NJOY with light water experimental transmission measurements at 293.6K with CONRAD code. The marginalization technique was applied to account for systematic uncertainties.
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Small-Angle Neutron Scattering study of solubilization of tributyl phosphate in aqueous solutions of L64 Pluronic triblock copolymers

Small-Angle Neutron Scattering study of solubilization of tributyl phosphate in aqueous solutions of L64 Pluronic triblock copolymers

Structure of pure L64 in D 2 O: Before characterizing the morphologies in presence of TBP, we have performed a structural study by Small Angle Neutron Scattering (SANS) of the pure aqueous copolymer solutions at 308 K. As one can see from the phase diagram in Fig. 1b, a transparent phase of pure copolymer L64 is formed in the absence of TBP. We have characterized the morphology of the aggregates by SANS in D 2 O for obvious contrast reasons, the average scattering length density of L64 being 0.43x10 10 cm -2 . The results are shown in Figure 2 for three different concentrations (0.2%wt, 5%wt, 10%wt), after subtraction of the unimer scattering for the two higher concentrations as explained below. At the highest dilution, which is below the cmc (≈0.35%wt, cf. supporting information SI) the scattering pattern I(q) is due to the individual unimers in solution. The low-q limit I o (0.023 cm -1 ) corresponds to a dry volume of 3300 Å 3 , and the radius of gyration, deduced from the Guinier fit - eq.(1) applied to unimers - in Fig.2, is 18.5 Å. Both values clearly correspond to individual molecules, which have a dry volume of 4640 Å 3 estimated from the molecular mass. The discrepancy may be due to the low scattered intensity in this case of scattering by individual molecules, but the order of magnitude remains correct.
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Covariance matrices of the hydrogen neutron cross sections bound in light water for the JEFF-3.1.1 neutron library

Covariance matrices of the hydrogen neutron cross sections bound in light water for the JEFF-3.1.1 neutron library

Abstract In the international neutron libraries, the behavior with the energy of the neutron cross sec- tions of hydrogen in light water depends on the thermal scattering laws tabulated in terms of S (α, β). For the Joint Evaluated Fission and Fusion library (JEFF), Mattes and Keinert have established thermal scattering laws by using the LEAPR module of the NJOY code. However, uncertainties on the corresponding S (α, β) were never reported. Such missing information was recently calculated with the nuclear data code CONRAD by determining the covariances between the model parameters involved in LEAPR. The obtained uncertainties were propagated to reac- tivity coe fficients calculated for critical assemblies operating in ”cold” conditions (temperature below 80 ◦ C) and for PWR in ”hot” operating conditions (300 ◦ C). For the integral benchmarks
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Optimization of Oil-in-Water Emulsion Stability: Experimental Design, Multiple Light Scattering, and Acoustic Attenuation Spectroscopy

Optimization of Oil-in-Water Emulsion Stability: Experimental Design, Multiple Light Scattering, and Acoustic Attenuation Spectroscopy

coalescence), if particle size is altered. Among the proper- ties enhancing emulsion stability, let us list: a low dispersed-phase volume fraction, a low density difference between phases, a low (but not too low) interfacial tension, a high viscosity of the continuous phase, a high mechanical resistance and elasticity of the interface, a high f potential, a high solubility of the emulsifier in the continuous phase (Bancroft’s rule), a narrow droplet size distribution. Increasing temperature often accelerates emulsion breaking. Except in special cases where spontaneous emulsification can occur, [9,10] and without neglecting the advantages of a lot of emulsification techniques, [11,12] mechanical agitation under turbulent flow regime remains the most common emulsification method, especially in large-scale operation. [12–16] Emulsification under mechan- ical agitation is described either by a kinetic model adapted to take into account the parameters of formulations or by a hydrodynamic approach better suited to describe the emul- sification process. [17] The formulation, properties and stab- ility of emulsions have been described throughout the literature. [18–21] As for the theoretical analysis and com- parison of emulsification processes, they have given rise to a few recent papers. [11,12,17,20,22] The present study aims at a better understanding of the effect of emulsifier and process variables on oil-in-water (O=W) emulsion proper- ties and behavior: droplet size distribution (DSD), viscosity, shelf stability and breakup modes, by evaluating and optimizing emulsifier properties and process para- meters in order to prepare the most stable (optimal) mixture. Emulsion stability will be monitored with two recently developed techniques (multiple light scattering and acoustic attenuation spectroscopy), still rarely used and providing immediately applicable practical guidelines for the control of emulsion properties.
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Study of neutron scattering in light water in the mistral experiments carried out in EOLE Reactor at CEA Cadarache

Study of neutron scattering in light water in the mistral experiments carried out in EOLE Reactor at CEA Cadarache

Key Words: light water, thermal scattering law, reactivity temperature coefficient, Mis- tral. 1. INTRODUCTION The Mistral experimental program [1], carried out in EOLE reactor at CEA Cadarache (France), was developed to test the feasibility of charging 100% MOX fuel in nuclear power plants. Among many neutronic parameters, it was measured the reactivity temperature coefficient (RTC) for the configurations Mistral-1 (UOX lattice), Mistral-2 and Mistral-3 (MOX lattices) between 10°C and 80°C.The interpretation of this parameter was performed with the Monte Carlo code TRIPOLI4 [2]. The nuclear data from JEFF-3.1.1 library [3] was used in the calculations.
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Light scattering in thin turbid tissue including macroscopic porosities: A study based on a Monte Carlo model

Light scattering in thin turbid tissue including macroscopic porosities: A study based on a Monte Carlo model

In this paper, a Monte Carlo Ray-tracing code based on large spheroid compounds is combined with an usual Multi-Layer Monte Carlo code in order to study the light propagation in turbid media (meso or microscopic heterogeneities) including several cavities (macroscopic heterogeneities). The cavities are made of spheroids, overlapping or not, whose sizes are larger than the mean free path of the turbid medium surrounding the cavities. This kind of system enables to characterize the light transport inside some biological tissues such as the fruit flesh or the porous bone (osteoporosis). From the transmitted and reflected flux generated by this modified Monte Carlo code, an average efficient scattering phase function and the time-resolved transmittance can be obtained. Several geometries and refractive indexes are tested. For instance, large samples mimicking bone tissue are used to explore the effect of the size of cavities on the retrieval of reduced scattering coefficient using the time-resolved diffusion solution. Moreover, the impact of a thin thickness on the apparent scattering coefficient is discussed. The goal of these simulations is also to consider how to use the reference method AD for such thin structures, this being related to the problem of the equivalence [ 1 , 18 ] between a porous medium and a homogeneous turbid medium. A simple relationship between optical depth and scattering phase function is proposed inside the code of an Adding-Doubling method to find equivalent scattering coefficient and scattering phase function from the data generated by the real porous turbid medium. Finally, experimental scattering phase functions obtained from apple tissues are considered and compared with those coming from a model with cavities.
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Assessment of the neutron noise induced by stationary fuel assembly vibrations in a light water reactor

Assessment of the neutron noise induced by stationary fuel assembly vibrations in a light water reactor

cross sections from the JEFF-3.1 library. Group constants are calculated by first homogenizing the geometry using an intermediate multi-group structure with g-groups, and then collapsed into few- group structure with G-groups using infinite-medium and B1 leakage-corrected neutron spectra. A simplified 2-D core design representative of an experimental light water reactor is used for the generation of the cross sections needed in the study. The core has 3x3 fuel assemblies, each assem- bly containing 17x17 pins fueled with UOX and surrounded by water. The vibrating fuel assembly is chosen to have a slightly lower enrichment (2.5% UOX) compared to the rest of the fuel assem- blies (3.7% UOX). This is done to ensure the changes in cross sections between the neighboring fuel assemblies are higher than their statistical fluctuations, when generating the cross sections with a Monte-Carlo code. In this work, diffusion coefficient, absorption cross section, removal cross section derived from the scattering cross section and ν-weighted fission cross sections in fast (G=1) and thermal (G=2) energy group with a cut-off at 0.625 eV are the input macroscopic data. The removal cross section is defined as the isotropic down-scattering cross section minus the isotropic up-scattering cross section weighted with the ratio between the thermal and the fast neutron fluxes. The parameter ν is the average number of neutrons emitted per fission. For the pin calculations, the cross section for the fuel and moderator are calculated separately, at the pin level, unlike the homogenization of the entire fuel assembly for calculation of nodal cross sections.
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Microstructure and concentration fluctuations in alcohol–Toluene and
alcohol-Cyclohexane binary liquids: A small angle neutron
scattering study

Microstructure and concentration fluctuations in alcohol–Toluene and alcohol-Cyclohexane binary liquids: A small angle neutron scattering study

3 and diluted monomers were prevailing for high and low values of x respectively (cf. Fig. 12 in ref. [10]). In this article, we extend the study of the segregation phenomenon towards a lower q- region. Small angle neutron scattering (SANS) is a complementary method to address the inhomogeneity of the mixtures in terms of concentration fluctuations, which are signatures of single-component-rich domains triggered by selective molecular interactions. Different hydrogenated/deuterated isotopic compositions are used to vary the scattering length density of the components of the binary liquids, and optimize the contrast between domains of different compositions. The characteristic correlation length of the inhomogeneities has been determined using the Ornstein-Zernike model [31]. An alternative approach, based on the Guinier approximation was applied, indicating that the observed inhomogeneity could be expressed in terms of weakly interacting spherical particles with diameter comparable to the H-bonded multimers [32]. The formalism of Bhatia and Thornton has been applied to decouple the different correlation functions related to density and concentration from the total neutron structure factor at zero-q [33]. The fluctuations of the local composition have been quantified by the evaluation of the Kirwood-Buff integrals (KBI), which can be determined from the experimental forward scattering intensities [34].
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Water Dynamics in Shewanella oneidensis at Ambient and High Pressure using Quasi-Elastic Neutron Scattering

Water Dynamics in Shewanella oneidensis at Ambient and High Pressure using Quasi-Elastic Neutron Scattering

dynamics and relaxation processes over a wide range of momentum (Q) and energy (ħω) transfers at nano- to picosecond timescales relevant to cellular biology 7–9 . In our experiment these correspond to a spectral broadening of the elastic line exceeding the energy resolution by a few tenths of meV. Therefore, the dynamics probed by QENS are readily distinguished from vibrational excitations or events such as enzyme catalysis that occur on significantly faster (fs) or slower (ms) timescales, respectively. QENS signals arise from incoherent scattering processes. Because of the large differences in H/D neutron scattering cross sections, isotopic contrast experiments can be designed to focus on the dynamics occurring within specific regions of the biological cell, including the intracellular medium (Im) or across membrane structures. QENS has already been developed to study high pressure effects on dynamic
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Two-dimensional neutron scattering in a floating heavy water bridge

Two-dimensional neutron scattering in a floating heavy water bridge

electric field lines without breaking of the local tetrahedral symmetry. The experiment is carried out by neutron scattering on a D 2 O bridge. Introduction In 1893 Sir William Armstrong placed a cotton thread between two wine glasses filled with chemically pure water. After applying a high voltage, a watery connection formed between the two glasses, and after some time, the cotton thread was pulled into one of the glasses, leaving, for a few seconds, a rope of water suspended between the lips of the two glasses [1]. As gimmick from early days of electricity this experiment was handed down through history until the present authors learned about it from W. Uhlig, ETH Zürich [2]. Although easy to reproduce, this watery connection between the two beakers, which is further referred to as 'floating water bridge' or ‘floating heavy water bridge’ in the case of D 2 O, respectively, holds a number of interesting static and dynamic phenomena [3-8].
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Neutron scattering study of adsorption in porous MCM-41 silica

Neutron scattering study of adsorption in porous MCM-41 silica

We will finally comment on the 1/Q underlying trend of diffracted intensity. This component of scattering, seen as a straight line of slope –1 in a log–log plot (inset in Fig. 2), is the signature of scattering from a powder sample that con- tains phase-correlated regions within which the scattering- length density fluctuates in two orthogonal directions but re- mains constant in the third direction. Given that our sample is prepared from a template material that forms long parallel cylinders it is not surprising to have this component of scat- tering. Re-plotting all our data on the log–log plot shows that the 1/Q component exists at every pressure, increases and passes through a maximum as the pores in the MCM- 41 are filled and reduces back approximately to the initial magnitude at the end of filling, i.e., it persists even when the pores are filled. Therefore, we conclude the 1/Q compo- nent does not originate from the pores themselves — if so, it would have been wiped out or greatly reduced when the pores are filled with a contrast-matched material. The 1/Q component is a measure of lateral (i.e., perpendicular to the cylindrical axis of the pores) correlations that are beyond the mesopore structure. They may be features caused by imper- fect hexagonal packing or by inaccessible pores that are ran- domly distributed throughout the lattice. We cannot speculate much further except to recognize that these are the correlations not affected by the presence of pentane for 8 days, nor by traversing the adsorption–desorption cycle once.
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Dynamics in hydrated inorganic nanotubes studied by neutron scattering: towards nanoreactors in water

Dynamics in hydrated inorganic nanotubes studied by neutron scattering: towards nanoreactors in water

samples have internal radii equal to 7.5 and 9.8 ˚A, respectively. By working under well-defined relative humidity (RH) values, water dynamics in IMO-OH was revealed by quasi-elastic spectra as a function of the filling of the interior of the tubes. When one water monolayer is present on the inner surface of the tube, water molecules can jump between neighboring Si –OH sites on the circumference by 2.7 ˚A. A self-di ffusion is then measured with a value (D ¼ 1.4  10 5 cm 2 s 1 ) around half of that in bulk water. When water molecules start filling also the interior of the tubes, a strong confinement effect is observed, with a con finement diameter (6 ˚A) of the same order of magnitude as the radius of the nanotube (7.5 ˚A). When IMO-OH is filled with water, the H-bond network is very rigid, and water molecules are immobile on the timescale of the experiment. For IMO-OH and IMO-CH 3 , motions of the hydroxyl groups are also
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Deeply virtual Compton scattering off the neutron

Deeply virtual Compton scattering off the neutron

(GPDs) particularly sensitive to E q , the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced. PACS numbers: 13.60.Fz, 13.85.Hd, 14.20.Dh, 14.65.-q Understanding the structure of the nucleon in terms of quarks and gluons is a central project of modern hadronic physics. In the non-perturbative regime relevant to nu- clear scales, Quantum Chromodynamics (QCD), the the- ory describing the elementary dynamics of the nucleon, is not yet solvable and remains rather mysterious. The electromagnetic probe provides an outstanding tool to study the nucleon structure. In this letter, we present the first study of the (~e, e ′
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Dynamic light scattering study of the ultrasonication of P(VDF-TrFE): A new model

Dynamic light scattering study of the ultrasonication of P(VDF-TrFE): A new model

CAC: critical aggregation concentration NZS: Zetasizer Nano ZS Introduction During the past few years, the copolymer poly(vinylidene difluoride-trifluoroethylene) P(VDF-TrFE) has attracted a growing interest, mainly because of its ferroelectric, pyroelectric and dielectric properties. Indeed, its high dielectric constant is useful in a large range of capacitor applications [1]. To improve the dielectric constant and thus the capacitance, or its ferroelectric properties, extensive research on P(VDF-TrFE) was carried out as it is but also as a matrix for nanocomposites [2]. These nanocomposites were prepared by incorporating various nanoparticles (NPs) in P(VDF-TrFE) in order to obtain reinforced materials with better mechanical properties or to add new properties to the matrix such as piezoelectric or nonlinear optical properties [3–6] .In these materials, the ultrasonication step is crucial. A good dispersion of nanoparticles is necessary to strengthen mechanical properties of the material, such as the elastic constant. This was observed for various polymers and even in oligomers[3–6].The goal of the dispersion, performed by ultrasonication, is generally to break the agglomerates of NPs, and,in the process, to decrease their hydrodynamic volume, which is the apparent volume occupied by a spherical (organic or inor
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Morphology of comb-shaped proton exchange membrane copolymers based on a neutron scattering study

Morphology of comb-shaped proton exchange membrane copolymers based on a neutron scattering study

Structural Parameters from the T-S Model. The T-S scattering function reveals important local structures about the PEMs. The best-fitting correlation length, ξ, decreases, while the domain periodicity, d, increases with increased hydrophilic side-chain fraction. Studies on the shift of the ionomer peak of Nafions follow the same trend as that of the current PEM samples, i.e., moving toward lower q with increased hydra- tion. 1–8 The previous explanation was that this was caused either by a swelling of ionomer clusters (in the core-shell model) 2,3 or by a swelling of ionomer spacing. 4,5 The T-S model agrees more with the latter, yet assuming a random distribution of the ionomers clusters (presumably in water channels) similar to microemulsion in contrast to the constrained locally ordered ionomers. 4 Teubner and Strey confirmed that the value of ξ/d increased with surfactant concentration in the case of micro- emulsion. 18 In this comb-shaped PEM, the side-chain sulfonic acid groups seemingly serve a similar function of a surfactant bridging the polymer backbone (oil phase) and waterssequestering the interface of water channel and polymer matrix. However, a lower value of ξ/d of PEM-32 is obtained from the best-fitting result (in Table 2). This can be rationalized if the contrast of the “ionomer peak” arises from the side-chain-rich regions and embedded water-rich ionomers (as shown in Figure 6d). Then, ξ/d is expected to decrease with increased volume fraction of hydrophilic side chains.
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Light scattering from cold rolled aluminum surfaces

Light scattering from cold rolled aluminum surfaces

Keywords: Scattering; Roughness; Fractal; Self-ane; Aluminum Since an early paper by Berry in 1979 [1], the study of wave scattering from self-ane (fractal) surfaces has become very active, see Refs. [2±10] for recent references. Most of these papers consist in numerical simulations; apart from the early works of Jakeman [11] and Jordan et al. [12] very few theoretical results have been published; the same statement stands for experimental results while lots of real surfaces [13±15] have been shown to obey scale invariance. Here we try and test ex- perimentally recent theoretical expressions ob- tained for the scattering of a scalar wave from a perfectly conducting self-ane surface [16]. We report scattering measurements of an s-polarized electromagnetic wave (632.8 nm) from a rough aluminum alloy plate (Al 5182). The latter was obtained by industrial cold rolling. As presented in
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Applications of Neutron and X-ray Scattering to the Study of Biologically Relevant Model Membranes

Applications of Neutron and X-ray Scattering to the Study of Biologically Relevant Model Membranes

functions, such as the photo cycle ( Luecke et al., 1999b ) and signal transmission. 8. Concluding remarks Diffraction techniques, especially with regards to X-rays, have traditionally been used to determine the structure of 3D crys- tals. Over the past decades, X-ray diffraction has been used to elucidate the structure of a wide range of materials to atomic res- olution – starting with common table salt in 1914. However, a few decades ago nobody could have envisioned that diffraction tech- niques would develop to an extent that they would successfully characterize the physical properties of disordered materials, such as biomimetic membranes. In this review we have presented some of the latest research regarding the application of X-ray and neutron scattering methods to elucidate the material properties previously thought to be the domain of other techniques (e.g. NMR and Raman spectroscopies, optical and electron micrscopies, etc.). Over the next decade, as some of the techniques discussed here and others (e.g. MD simulations, various optical microscopies, to name but a few) reach maturity, we will for the first time have unique access to the much touted structure–function relationship that is universally sought out in biology.
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Light scattering from cold rolled aluminum surfaces

Light scattering from cold rolled aluminum surfaces

These first results can be considered as very promising: let us recall that we assumed the surface to be purely one-dimensional and perfectly conducting and that we used a basic Kirchhoff approximation, neglecting all shadowing or multiple scattering effects... Refining the modeling of shadowing or multiple scattering in the specific case of self-affine surfaces could allow to design a valuable tool to measure the geometrical parameters describing self-affine surfaces. This experimental study also makes clear that self-affine correlations can be a relevant formalism to describe the optical properties of real surfaces. Beyong classical optical phenomena this could be also of great interest in the context of the recent studies [23, 24] modeling thermal emission properties of rough surfaces.
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Theoretical study of light scattering and emission from dense ensembles of resonant dipoles

Theoretical study of light scattering and emission from dense ensembles of resonant dipoles

In the previous chapter we studied light scattering from a cloud of cold atoms. Although the atomic cloud we study is much more dilute than the sky, we have seen that resonant light scattering from a cold wavelength-size atomic cloud is very dierent from Rayleigh scattering. We have discussed in the last two chapters that the reason for this lies in the presence of strong resonant dipole-dipole interactions in the system under study. We have seen that as the atomic density increases, light scattering changes from a purely diusive to a partially diusive and partially diractive regime. In the latter regime, light scattering from the cloud occurs as if the cloud were an object that is described by an eective refractive index. When a nite-size object is described by an index of refraction that is dierent from its optical environment, the object is known to diract light. Apart from this macroscopic point of view of light scattering, we can also interpret diraction in another way: what happens at a microscopic level that makes the atomic cloud diracting light? A similar question would be: what is the physical origin at the microscopic level of the index of refraction, which is a macroscopic notion, and makes an object diracting light? It is in this chapter that we study the connection between a microscopic and macroscopic description of an ensemble of homogeneously broadened scatterers. However, the conclusions drawn in this chapter are expected to be correct as well for inhomogeneously broadened systems like a dense ensemble of quantum dots. Apart from Section 4.8 , this chapter has been adapted from our recently published paper, called Polaritonic modes in a dense cloud of cold atoms [ 67 ].
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Coherence effects in scattering order expansion of light by atomic clouds

Coherence effects in scattering order expansion of light by atomic clouds

been realized for N = 500 atoms with b 0 = 5, standard deviation σ R = 17.32/k and for two different detuning, δ = 4.5 and δ = 0, corresponding to b(δ) = 0.061 and b(δ) = 5, respectively. For the case of small optical thick- ness (b(δ) = 0.061), the field decreases as the scattering order n increases, and the series (11) converges. For the case of larger optical thickness (b(δ) = 5), the presence of eigenvalues of modulus larger than unity makes the multiple scattering series diverge. Hence, in presence of above-unity eigenvalues of G, the multiple scattering de- scription loses its validity: for sufficiently dense media, due to the long-range interaction of the Green’s func- tion, the build-up of the scattered radiation field cannot be seen as the sum of interactions involving an increas- ing number of atoms, and the local iteration of the scat- tering event described by Eq.(10) is no longer possible. Instead, the total scattered field is a result of a global in- teraction with the entire sample. Let us remark that the criterion of all eigenvalues having modulus below unity for the convergence of the series is in agreement with the results of Ref.[28]. A detailed study of the typical spec- trum of the linear operator in (10) has been proposed in [29], yet it is important to mention that the spectrum exhibits strong fluctuations from one realization to an- other. Since the multiple scattering process corresponds to a geometric series, the radiated power grows or de- creases as a power-law of the largest eigenvalue of the linear operator in Eq.(10) for large n.
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