Dipolar coupling

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Cross-Correlated Relaxation of Dipolar Coupling and Chemical-Shift Anisotropy in Magic-Angle Spinning R 1ρ NMR Measurements: Application to Protein Backbone Dynamics Measurements

Cross-Correlated Relaxation of Dipolar Coupling and Chemical-Shift Anisotropy in Magic-Angle Spinning R 1ρ NMR Measurements: Application to Protein Backbone Dynamics Measurements

(i.e. with a single orientation within the rotor-fixed frame) should show mono-exponential decays. However, we find that also when using single crystallites rather than a powder distribution the decay is bi-exponential (data not shown), pointing to an additional mechanism. This second possible origin of non-exponential decay is the presence of cross-correlated relaxation due to 15 N-CSA/ 1 H- 15 N dipolar-coupling interference. When observing the two components of the

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Measurement of the dynamical dipolar coupling in a pair of magnetic nano-disks using a Ferromagnetic Resonance Force Microscope

Measurement of the dynamical dipolar coupling in a pair of magnetic nano-disks using a Ferromagnetic Resonance Force Microscope

Studies of the collective dynamics in magnetic nano- objects coupled by the dipolar interaction has recently attracted a lot of attention [1–8] due to its potential for creating novel properties and functionalities for the infor- mation technology. It affects the writing time of closely packed storage media [9], the synchronization of spin transfer nano-oscillators [10], and more broadly the field of magnonics [11], which aims at using spin-waves (SW) for information process [12]. Despite the generic na- ture of the dynamic magneto-dipolar interaction, which is present in all ferromagnetic resonance phenomena, its direct measurement has been elusive because it is diffi- cult to reach a regime where this coupling is dominant. It requires that the strength of the dynamical coupling Ω exceeds both the deviation range of eigen-frequencies between coupled objects and the resonance linewidth. Large Ω are usually obtained by fabricating nano-objects having large magnetization and placed nearby. But the constraint of fabricating two nano-objects, whose SW modes both resonate within Ω, is difficult to meet. For long wavelengths, the SW eigen-frequency is indeed very sensitive to imperfections in the confinement geometry, inherent to uncertainties of the nano-fabrication process. Moreover, a direct determination of the coupling strength between any two systems, as for instance a superconduct- ing qubit and electronic spins [13], requires the ability to tune and detune them at least on the Ω-range. So far, the absence of a knob to do so with the individual frequen- cies of nearby magnetic objects has prevented a reliable measurement of the dynamical dipolar coupling.
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Finite-size corrections in simulation of dipolar fluids

Finite-size corrections in simulation of dipolar fluids

observed N dependence is in very good agreement with the theoretical predictions for the finite-size corrections of different origins: the explicit corrections due to the absence of fluctuations in the number of particles within the canonical simulation and the implicit corrections due to the coupling between the environment around a given particle and that around its images in the neighboring cells. The latter dominate in fluids of strong dipolar coupling characterized by low compressibility and high dielectric constant. The ability to clean with great precision the simulation data from these corrections combined with the use of very powerful anisotropic integral equation techniques means that exact correlation functions both in real and Fourier spaces, Kirkwood-Buff integrals and bridge functions can be derived from box sizes as small as N≈100, even with existing long-range tails. In presence of dielectric discontinuity with the external medium surrounding the central box and its replica within the Ewald treatment of the coulombic interactions, the 1/N dependence of the g mnl (r) is
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Bridge function for the dipolar fluid from simulation

Bridge function for the dipolar fluid from simulation

MC/HNC and MC/MSA treatments are identically "exact" with the choice r max,MC =5. Moreover, the function c+v clearly vanishes faster than b in the intermediate region r=2-5 for this high dipolar coupling. To the author's knowledge, this important observation could not be anticipated from theoretical arguments. On one side, it is well known that the bare MSA closure, of linearized nature, gives very bad results at high  *2 while the bare HNC closure behaves quite well; so, the opposite trend c+v>>b applies near the first peak. On the other side, in absence of known theoretical asymptotic law, one could just say that an expansion of (1) gives c+v≈b+½h 2 … for the tail. At large distances, if h 2 <<b, then c+v and
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Optimizing magneto-dipolar interactions for synchronizing vortex based spin-torque nano-oscillators

Optimizing magneto-dipolar interactions for synchronizing vortex based spin-torque nano-oscillators

In a previous work 21 , 22 , we studied the capability of two vortex-based STNOs to synchronize through dipolar coupling. In this first approach, we have only considered the case of two vortices with identical polarities and chi- ralities, and already demonstrated the possibility to ob- serve synchronization. In this new study report, we show that changing the relative polarity and chirality param- eters will strongly modify the interaction between the auto-oscillators and may strongly modify the efficiency

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The Random Fuse Network as a Dipolar Magnet

The Random Fuse Network as a Dipolar Magnet

burns. The dipolar coupling then relieves its longitudinal neighbors while further stressing its transverse neighbors, who burn in turn, and a stripe of burnt fuses develops, eventually spanning the whole system (the network then stops conducting and the formation of additional stripes is consequently prohibited). At high (wide) disorder, a resilient fuse in the passage of a burnt stripe will stop the growth of the crack, and new cracks will nucleate elsewhere. This suggest a transition, upon increase of the disorder [7,9,26], from an abrupt regime characterized by the growth of a single macroscopic unstable crack to a continuous regime in which the system is significantly damaged before its global failure.
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1,3-Dipolar cycloadditions with azomethine ylide species generated from aminocyclopropanes

1,3-Dipolar cycloadditions with azomethine ylide species generated from aminocyclopropanes

1. Introduction 1,3-Dipolar cycloaddition reactions constitute a general and versatile tool for the synthesis of five- membered ring heterocycles. 1 Among the various 1,3-dipoles that can be used, azomethine ylides 1 have led to a number of interesting applications, as they can provide access to diversely substituted pyrrolidines, as well as to oxazolidines and imidazolidines. 2 A number of methods have been developed for the generation of these dipoles, among which one of the most popular relies on the deprotonation of iminium species 2 featuring acidic hydrogens at the α position relative to the nitrogen atom (Scheme 1, equation 1). 3 Since the protonation of bicyclic aminocyclopropanes 3 is an efficient and original route for the generation of iminium cations 4 (equation 2), 4 we envisioned that the derivatives 5 could be suitable precursors to cyclic azomethine ylides 6 (equation 3).
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A tunable magnetic metamaterial based on the dipolar four-state Potts model

A tunable magnetic metamaterial based on the dipolar four-state Potts model

9 this ferromagnetic configuration and not to properties of individual spins. For instance, in the case of 𝛼 = 22.5°, the proportion of ferromagnetic domains drops from 73% to 20% when the period of the lattice is increased from 500 to 700 nm, which corresponds to the reduction of the dipolar interactions by a factor of 2.7 (see SI4). The high temperature dynamics is also revealed by the orientation of the configurations. For 𝛼 = 0° (figure 2.a), the antiferromagnetic domains are mostly aligned perpendicularly to the initial saturation direction. For 𝛼 = 45°, the size of the spin-ice domains is limited by the number of spins opposite to the initial saturation direction, which is quite small at 12%. This indicates that the reversal of spins proceeds by a 90° rather than 180° rotation. The presented thermal procedure is therefore not fully efficient. The system does not explore the entire energy landscape and is trapped in a local energy minimum. Nevertheless, the system can be driven in domains of the expected low energy configurations. It is interesting to compare the energy scales of the four-state dipolar Potts model at 45° from a square lattice and the most studied square Ising ice. The ground state is identical for both systems (type I vertices). It can be reached almost perfectly in the square Ising ice via a superparamagnetic regime [ 26 ]. But the energy difference between the two lowest energy states (type I and type II vertexes) is about 10 times the one between the two lowest energy states of the Potts system (considering a dipolar approximation). Achieving a perfect thermalization of the dipolar Potts system remains a challenge.
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Derivation of the time-dependent Gross-Pitaevskii equation for the dipolar gases

Derivation of the time-dependent Gross-Pitaevskii equation for the dipolar gases

(1) and (4) are close in L 2 -norm as is stated in Proposition 1 below. For the truncated dipolar potential, we also have [14] the existence for all 1 < p < ∞ of some constant C p independent of R > 0 such that for all f ∈ L p (R 3 ), k(1 |x|>R K) ∗ fk L p (R 3 ) ≤ C p kfk L p (R 3 ) . The regularity of the solutions of (1) and (4) has already been well studied. But since (1) depends on N , one has to make sure that the Sobolev norms of the solution can be bounded independently of N . We do so in the following proposition which is an easy adaptation of [6, Proposition 3.1].
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Domain decoration in dipolar coupled ferromagnetic stacks with perpendicular anisotropy

Domain decoration in dipolar coupled ferromagnetic stacks with perpendicular anisotropy

V. Baltz, B. Rodmacq, and B. Dieny SPINTEC, URA CNRS/CEA 2512, CEA-Grenoble, 38054 Grenoble Cedex 9, France 共Received 29 December 2004; accepted 21 February 2005; published online 29 March 2005兲 The dipolar stray field effects between two nonuniformly magnetized ferromagnetic Co/ Pt stacks with perpendicular anisotropy are investigated by polar magneto-optical Kerr effect microscopy. Decoration of a reversed domain in the hard stack by a domain ring in the soft stack is evidenced and interpreted by magnetostatic calculations. Mirrored 360° domain walls are strongly stabilized by these interactions. © 2005 American Institute of Physics. 关DOI: 10.1063/1.1897845兴
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Spatially periodic domain wall pinning potentials: Asymmetric pinning and dipolar biasing

Spatially periodic domain wall pinning potentials: Asymmetric pinning and dipolar biasing

cleaned using an argon plasma. Starting from the substrate, each film consists of a Pt buffer layer, a Co layer or Co/Pt/ Co stack, a Pt spacer layer, and an upper Co/Pt multilayer stack (see Table I ). The individual Co layers within each stack are coupled ferromagnetically across thin Pt layers (1.6 or 1.8 nm), which ensures a cooperative magnetic reversal of the layers. 22 , 31 – 33 The lower, ultrathin, magnetically soft Co layer structure is separated from the upper stack by a 5 nm thick Pt spacer layer. As such, the effective fields 34 associ- ated with interlayer exchange and dipolar “orange peel” cou- pling are weak (on the order of or less than 1 Oe) and in the final structure are dominated by the strong dipolar fields of the nanoplatelets (see Sec. II B ).
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Uniqueness of mainly dipolar magnetic fields recovered from directional data

Uniqueness of mainly dipolar magnetic fields recovered from directional data

If it is known to have monopole sources (such as in the case of the gravitational field), then the maximum dimension of the space and cone of solutions of the unsign[r]

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Coherent control of dipolar coupled spins in large Hilbert spaces

Coherent control of dipolar coupled spins in large Hilbert spaces

For our sensitivity measurements, we design two multiple-pulse control techniques (based on coherent averaging theory) - one that suspends all spin interactions in the syst[r]

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Complexes of dipolar excitons in layered quasi-two-dimensional nanostructures

Complexes of dipolar excitons in layered quasi-two-dimensional nanostructures

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignemen[r]

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Effect of substitution on the intramolecular 1,3-dipolar cycloaddition of alkene tethered münchnones

Effect of substitution on the intramolecular 1,3-dipolar cycloaddition of alkene tethered münchnones

guillaume.belanger@usherbrooke.ca ReceiVed July 27, 2006 A sequence of chemoselective activation of N-acylaminoacids, mu¨nchnone generation, intramolecular 1,3-dipolar cycloaddition, and ring opening efficiently generated functionalized polycyclic structures such as cyclopenta[b]pyrroles or zwitterionic bicyclo[4.3.0]nonane or bicyclo[3.3.0]octanes in one operation is given. These zwitterionic species were isolated for the first time and were subsequently reduced to bicyclic aminoalcohols. The effect of the substitution of both the dipolarophile and the mu¨nchnone on the intramolecular cycloaddition outcome was examined. It was found that either nonactivated or electron- poor alkenes can react with the mu¨nchnone if these alkenes are tethered at position 4 on the mu¨nchnone ( 2, R 2 ) alkene tether), whereas only an electron-poor alkene at position 2 ( 2, R 3 ) alkene tether) could undergo successful cycloaddition. Also, mu¨nchnones substituted at position 2 with a phenyl ( 2, R 3 ) Ph) showed a dramatic increase in reactivity, whereas a phenyl at position 4 ( 2, R 2 ) Ph) had a very limited effect.
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Phase diagram of a three-dimensional dipolar model on an fcc lattice

Phase diagram of a three-dimensional dipolar model on an fcc lattice

FIG. 11. Anisotropy, a) and dipolar, b) components of the heat capacity. In the RAD case the total capacity includes only the C dip component. Symbol: L = 7 for λ u ≤ 4 and L = 4 otherwise. Solid blue lines for λ u ≤ 4: L = 4. IV. CONCLUSION In this work, we have determined a significant part of the magnetic phase diagram of an ensemble of dipoles with uniaxial anisotropy located on the nodes of a FCC lattice from tempered Monte Carlo simulations. This is motivated first by the search for the conditions under which a super-ferromagnetic phase induced by DDI can be reached in the supra-crystals of MNP synthesized experimentally, and more generally by the determination of the nature of the ordered low temperature phase in these systems. The nature of the low temperature ordered phase is found successively FM and SG with increasing the MAE strength. From the behavior of m 2 with respect to L at low T ∗
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On the Coupling between Ionic Conduction and Dipolar Relaxation in Deep Eutectic Solvents: Influence of Hydration and Glassy Dynamics

On the Coupling between Ionic Conduction and Dipolar Relaxation in Deep Eutectic Solvents: Influence of Hydration and Glassy Dynamics

physical information on the samples and have been excluded from the discussion. In the low temperature range, typically below 210 K, a main peak appeared in the dielectric loss. It was also associated to a jump in the real permittivity ´, as indicated by solid lines and red filled areas in Fig. 1(a) and (b). This was attributed to the dipolar -relaxation process, in agreement with the

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Water-mechanical property coupling

Water-mechanical property coupling

2 Plasticization Effects on the Multi-Scale Internal Stresses This work investigates the plasticization effects related to the evolution, as a function of the moisture content, of the hygro-elastic properties on the internal stress states during the transient part of a hygroscopic load. The proposed approach involves the coupling of the classical continuum mechanics formalism presented by Jacquemin and Vautrin [ 5 ] to Eshelby-Kröner self-consistent scale transition model recently extended to account for a hygroelastic load [ 4 , 6 , 7 ]. An inverse scale transition model provides, from the experimental macroscopic ply moduli (Table 1 ), the evolution of the local hygro-elastic properties experienced by the epoxy matrix as the moisture diffusion takes place. Figure 1 shows the moisture diffusion process inside a composite structure following a Fickian behavior. According to Fig. 2 , the fact of considering the plasticization and thus an evolution of the hygro-elastic properties of both the composite plies and its constitutive matrix strongly affects the transverse stresses levels and their distributions in the plies and their constituents.
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MOMA GC-MS Coupling

MOMA GC-MS Coupling

Instrumental Suite: The French brassboard GC coupled has been coupled to the US brassboard ion trap mass spectrometer in a flight-like configuration (fig 1) for the coupling campaign. The MOMA GC setup is based on the Sample Analysis at Mars (SAM) heritage design with a He reservoir and 4 separate ana- lytical modules including traps, columns and TCDs. Solid samples are sealed and heated in this setup using the manual tapping station (fig. 1), design and built at MPS in Germany, for GC-MS analysis. Then the ef- fluent is ionized by an electron impact ionization source in the MS chamber and analyzed by the linear ion trap mass spectrometer (fig. 1).
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Coupling, Reinforcement, and Speciation

Coupling, Reinforcement, and Speciation

(i.e., where clines overlap). When there is LD, direct selection on each locus is supplemented by indirect selection as a re- sult of association with the other locus. This effect is asym- metrical and makes the clines move toward one another until their centers are coincident. Each cline is steepened by this process because each locus experiences stronger selection (direct 1 indirect). Thus, both the genomically local and overall barriers to gene flow are increased, potentially gen- erating strongly stepped clines for loci throughout the ge- nome (as in Bombina; Szymura and Barton 1991). Where this occurs, hybrid zones present a strong barrier to gene flow (Barton and Gale 1993), in marked contrast to hybrid zones where selection is weaker relative to recombination and coupling does not occur (e.g., Chorthippus parallelus; Shuker et al. 2005). The process of attraction between clines is an example of adaptive coupling of existing barrier effects ( fig. 1B, I). We distinguish it from by-product coupling pro- cesses because selection acts directly to cause coupling. In this case, coincidence of two clines is equivalent to an in- crease in LD between a pair of loci: it reduces the number of un fit heterozygous genotypes produced and so increases overall mean fitness. This component of selection is distinct from that operating to maintain clines at the individual loci. Because it increases mean fitness, coupling can be consid- ered adaptive —hence the term “adaptive coupling.”
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