Journal articles: 'Dipolar'

1

Mikhailov, Ivan V., Victor M. Amoskov, Anatoly A. Darinskii, and Tatiana M. Birshtein. "The Structure of Dipolar Polymer Brushes and Their Interaction in the Melt. Impact of Chain Stiffness." Polymers 12, no. 12 (December 2, 2020): 2887. http://dx.doi.org/10.3390/polym12122887.

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By using the numerical lattice Scheutjens–Fleer self-consistent field (SF-SCF) method we have studied the effect of the restricted flexibility of grafted chains on the structure and mutual interaction of two opposing planar conventional and A-type dipolar brushes. Brushes are immersed in the solvent consisting of chains similar to the grafted ones. The increase of the chain rigidity enhances the segregation of grafted chains in a A-type dipolar brush into two populations: backfolded chains with terminal monomers near the grafting surface and chains with the ends at the brush periphery. The fraction of backfolded chains grows by an increase of the Kuhn segment length. It is shown that two opposite A-type dipolar brushes from semi-rigid chains are attracted to each other at short distances. The attraction becomes more pronounced and begins at larger distances for more rigid chains with the same brush characteristics: polymerization degree, grafting density, and dipole moments of monomer units. This attraction is connected with the dipole-dipole interactions between chains of oncoming brushes with oppositely directed dipoles penetrating deeply into each other upon contact. This effect of the chain rigidity is opposite to that for conventional brushes without dipoles in the chains. For such brushes, an increase in the chain rigidity leads to the enhanced repulsion between them.

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Kusmartsev, F. V., and M. Saarela. "Dipolar clusters and ferroelectricity in high Tc superconductors." International Journal of Modern Physics B 29, no. 25n26 (October 14, 2015): 1542002. http://dx.doi.org/10.1142/s0217979215420023.

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In this paper, we show that doping of hole charge carriers induces formation of resonance plaquettes (RPs) having electric dipolar moments and fluctuating stripes in cuprates. A single RP is created by many-body interactions between the dopant ion or a charge fluctuation outside and holes inside the CuO plane. In such a process, Coulomb interacting holes in the CuO plane are self-organized into four-particles resonance valence bond plaquettes bound with dopants or polarons located in the spacer layer between CuO planes. Such RPs have ordered and disordered phases. They are ordered into charge density waves (CDW) or stripes only at certain conditions. The lowest energy of the ordered phase corresponds to a local antiferroelectric ordering. The RPs mobility is very low at low temperatures and they are bound into dipole–dipole pairs. Electromagnetic radiation interacts strongly with RPs electric dipoles and when the sample is subjected to it, the mobility changes significantly. This leads to a fractal growth of dipolar RP clusters. The existence of electric dipoles and CDW reveal a series of new phenomena such as ferroelectricity, strong light and microwave absorption and the field induced superconductivity.

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Downing, Charles A., and Luis Martín-Moreno. "Polaritonic Tamm states induced by cavity photons." Nanophotonics 10, no. 1 (September 14, 2020): 513–21. http://dx.doi.org/10.1515/nanoph-2020-0370.

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AbstractWe consider a periodic chain of oscillating dipoles, interacting via long-range dipole–dipole interactions, embedded inside a cuboid cavity waveguide. We show that the mixing between the dipolar excitations and cavity photons into polaritons can lead to the appearance of new states localized at the ends of the dipolar chain, which are reminiscent of Tamm surface states found in electronic systems. A crucial requirement for the formation of polaritonic Tamm states is that the cavity cross section is above a critical size. Above this threshold, the degree of localization of the Tamm states is highly dependent on the cavity size since their participation ratio scales linearly with the cavity cross-sectional area. Our findings may be important for quantum confinement effects in one-dimensional systems with strong light–matter coupling.

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Hooshmand, Nasrin, Justin A. Bordley, and Mostafa A. El-Sayed. "Breakdown of the Dipole-Dipole Approximation at Short Distances and Hot Spot Formation between a Pair of Silver Nanocubes." MRS Proceedings 1802 (2015): 19–24. http://dx.doi.org/10.1557/opl.2015.504.

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ABSTRACTAg or Au nanocubes are known to be plasmonic nanoparticles with strong plasmonic fields concentrated around their corners1. When these nanoparticles aggregate the individual plasmonic oscillations of each particle begin to couple. The coupling between the two plasmonic nanoparticles is assumed to be dipolar in nature which results in an exponential red shift dependence of their localized surface plasmon resonance (LSPR) on the dimer separation2. Unfortunately, this exponential behavior is shown to fail as the separation distance between the two 42 nm nanocube dimer becomes 6nm or smaller3. Hooshmand et al4 have noted that these separation distances are marked by the formation of hot spots between the facets of the dimer.This dipolar exponential behavior results from a treatment of the coupling between the two excited nanocubes as a coupling between two oscillating dipole moments2. As a result, the vectorial addition of all the oscillating electronic dipoles is assumed to interact with the nearest nanoparticle as a single oscillating electronic dipole. Herein we suggest that as the separation distance becomes increasingly small, the coupling between the individual oscillating dipoles on the different nanocubes becomes significant. Thus, the dipolar exponential behavior fails to accurately predict the near field coupling between two nanoparticles with small separation distances.This leads to the realization that the interaction between the individual oscillating dipoles on the two nanocubes changes in a complicated manner as a function of separation distance. At 2nm, a good fraction of the oscillating dipoles are between the adjacent facets of the nanocubes as well as between the the corners. While at 3 nm less are in between the two facets of the nanocubes and a larger portion are localized at the corners. Thus, the coupling is not only dependent on the separation distance but also on what the separation does to the net interaction between the oscillating dipoles on each facet of the two coupled nanocubes. This results in the failure of the exponential behavior as the dipole moment on each nanocube is changing with distance in a complicated manner.

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Flór, J. B., and G. J. F. Van Heijst. "An experimental study of dipolar vortex structures in a stratified fluid." Journal of Fluid Mechanics 279 (November 25, 1994): 101–33. http://dx.doi.org/10.1017/s0022112094003836.

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This paper describes laboratory experiments on dipolar vortex structures in a linearly stratified fluid. The dipoles are generated by a pulsed horizontal injection of a small volume of fluid, by which a localized three-dimensionally turbulent flow region is created. After the subsequent gravitational collapse the flow becomes approximately two-dimensional, and eventually a single vortex dipole emerges, as the result of the self-organizing properties of such flows. The flow evolution has been visualized both by dye and tracer particles, through which qualitative as well as quantitative information was obtained. By application of digital image analysis, the spatial distribution of the velocity ν, vorticity ω and stream function ψ were determined. It was found that dipoles in the turbulent-injection experiments are characterized by a nonlinear sinh-like relationship between ω and ψ, whereas in the case of laminar injection the (ω, ψ)-scatter plots of the dipoles reveal a linear relationship. Notwithstanding these differences, both types of dipoles show a dynamical structure that agrees very well with the Lamb–Chaplygin dipole, as was found by comparing the size, position of maximum vorticity, cross-sectional distributions of ν and ω, characteristics of the (ω, ψ)-relationship, and the translation speed of the experimental and the model dipole.

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6

LI, QIU-YAN, ZHENG-WEI XIE, and ZAI-DONG LI. "QUANTUM PHASE TRANSITION OF DIPOLAR BOSONS IN OPTICAL LATTICES." International Journal of Modern Physics B 19, no. 21 (August 20, 2005): 3345–52. http://dx.doi.org/10.1142/s0217979205032152.

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In terms of the Green's function method we study the energy spectrum of dipolar boson atoms with the dipole-dipole interaction in an optical lattice. The Superfluid-Mott-Insulator phase transition condition of the dipolar bosons is determined from the energy-band structure of the excitation spectrum as a function of interatomic repulsion, dipolar bosons interaction and the tunnel coupling constants. The superfluid phase is explained explicitly from the energy spectrum derived in terms of the Bogoliubov approach as well.

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7

Monahan, Adam H., and John C. Fyfe. "How Generic Are Dipolar Jet EOFs?" Journal of the Atmospheric Sciences 66, no. 2 (February 1, 2009): 541–51. http://dx.doi.org/10.1175/2008jas2814.1.

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Abstract Dipolar structures arise as empirical orthogonal functions (EOFs) of extratropical tropospheric zonal-mean zonal wind in observations, in idealized dynamical models, and in complex general circulation models. This study characterizes the conditions under which dipoles emerge as EOFs of a jet of fixed shape f (x), which takes a unique localized extremum and is smooth but is otherwise arbitrary, characterized by fluctuations in strength, position, and width of arbitrary distribution. It is shown that the factors that influence the extent to which a dipolelike structure will arise as an EOF are (i) the skewness of position fluctuations, (ii) the dependence of position fluctuations on strength and width fluctuations, and (iii) the relative strength of the position and width fluctuations. In particular, the leading EOF will be a dipole if jet position fluctuations are not strongly skewed, not strongly dependent on strength and width fluctuations, and sufficiently large relative to strength and width fluctuations. Because these conditions are generally satisfied to a good approximation by observed and simulated tropospheric eddy-driven jets, this analysis provides a simple explanation of the ubiquity of dipolar jet EOFs.

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Khalyavin, Dmitry D., Roger D. Johnson, Fabio Orlandi, Paolo G. Radaelli, Pascal Manuel, and Alexei A. Belik. "Emergent helical texture of electric dipoles." Science 369, no. 6504 (August 6, 2020): 680–84. http://dx.doi.org/10.1126/science.aay7356.

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Long-range ordering of magnetic dipoles in bulk materials gives rise to a broad range of magnetic structures, from simple collinear ferromagnets and antiferromagnets, to complex magnetic helicoidal textures stabilized by competing exchange interactions. In contrast, dipolar order in dielectric crystals is typically limited to parallel (ferroelectric) and antiparallel (antiferroelectric) collinear alignments of electric dipoles. Here, we report an observation of incommensurate helical ordering of electric dipoles by light hole doping of the quadruple perovskite BiMn7O12. In analogy with magnetism, the electric dipole helicoidal texture is stabilized by competing instabilities. Specifically, orbital ordering and lone electron pair stereochemical activity compete, giving rise to phase transitions from a nonchiral cubic structure to an incommensurate electric dipole and orbital helix via an intermediate density wave.

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9

Bonardd, Sebastián, Viviana Moreno-Serna, Galder Kortaberria, David Díaz Díaz, Angel Leiva, and César Saldías. "Dipolar Glass Polymers Containing Polarizable Groups as Dielectric Materials for Energy Storage Applications. A Minireview." Polymers 11, no. 2 (February 13, 2019): 317. http://dx.doi.org/10.3390/polym11020317.

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Materials that have high dielectric constants, high energy densities and minimum dielectric losses are highly desirable for use in capacitor devices. In this sense, polymers and polymer blends have several advantages over inorganic and composite materials, such as their flexibilities, high breakdown strengths, and low dielectric losses. Moreover, the dielectric performance of a polymer depends strongly on its electronic, atomic, dipolar, ionic, and interfacial polarizations. For these reasons, chemical modification and the introduction of specific functional groups (e.g., F, CN and R−S(=O)2−R´) would improve the dielectric properties, e.g., by varying the dipolar polarization. These functional groups have been demonstrated to have large dipole moments. In this way, a high orientational polarization in the polymer can be achieved. However, the decrease in the polarization due to dielectric dissipation and the frequency dependency of the polarization are challenging tasks to date. Polymers with high glass transition temperatures (Tg) that contain permanent dipoles can help to reduce dielectric losses due to conduction phenomena related to ionic mechanisms. Additionally, sub-Tg transitions (e.g., γ and β relaxations) attributed to the free rotational motions of the dipolar entities would increase the polarization of the material, resulting in polymers with high dielectric constants and, hopefully, dielectric losses that are as low as possible. Thus, polymer materials with high glass transition temperatures and considerable contributions from the dipolar polarization mechanisms of sub-Tg transitions are known as “dipolar glass polymers”. Considering this, the main aspects of this combined strategy and the future prospects of these types of material were discussed.

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10

Fuentes, O. U. Velasco, and G. J. F. Van Heijst. "Experimental study of dipolar vortices on a topographic βT-plane." Journal of Fluid Mechanics 259 (January 25, 1994): 79–106. http://dx.doi.org/10.1017/s0022112094000042.

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The behaviour of dipolar vortices in a rotating fluid with a sloping bottom (simulating the variation of the Coriolis parameter on the Earth, with the direction of steepest bottom slope corresponding with the northern direction) has been investigated in the laboratory. Dipoles were generated by moving a vertical cylinder through the fluid. Dye photographs provided qualitative information, whereas quantitative information about the evolving flow field was obtained by streak photography. Dipoles initially directed under a certain angle relative to the west–east axis showed meandering or cycloid-like trajectories. Soeme symmetries between east-travelling dipoles (ETD's) and west-travelling dipoles (WTD's) were observed. ETD's are stable in the trajectory sense: a small deviation from zonal motion results in small oscillations around the equilibrium latitude. WTD's are unstable: small initial deviations produce large displacements in northern or southern directions. This asymmetry arises because the vorticity of a dipole moving westward is anticorrelated with the ambient vorticity, while the vorticities are correlated when the dipole moves eastward. ETD's increase in size and eventually split into two independent monopoles, the rate of growth depending on the gradient of planetary vorticity. WTD's are initially more compact but owing to the large displacements in the meridional direction strong asymmetries in the circulation of the two halves are produced, resulting in a large deformation of the weaker part. The experimental observations show good qualitative agreement with analytical and numerical results obtained using a modulated point-vortex model.

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11

Chan, Chin Han, and Hans-Werner Kammer. "Characterization of polymer electrolytes by dielectric response using electrochemical impedance spectroscopy." Pure and Applied Chemistry 90, no. 6 (June 27, 2018): 939–53. http://dx.doi.org/10.1515/pac-2017-0911.

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Abstract Authors present a phenomenological view on dielectric relaxation in polymer electrolytes, which is monitored by electrochemical impedance spectroscopy. Molecular interaction of polymer chains with salt molecules (or dipole-dipole interaction between segments and salt molecules) leads to dipolar molecular entities. Frequency-dependant impedance spectra are the key quantities of the interest for determination of electric properties of materials and their interfaces with conducting electrodes. Salt concentration serves as parameter. Bulk and interfacial properties of the samples are discussed in terms of impedance (Z*) and modulus (M*) spectra. We focus on two different classes of systems, i.e. high molar mass of poly(ethylene oxide) (PEO)+lithium perchlorate (LiClO4) (i.e. the inorganic salt) and epoxidized natural rubber (ENR-25) with 25 mol% of epoxide content+LiClO4. Impedance spectra with salt content as parameter tell us that we have interaction between dipolar entities leading to dispersion of relaxation times. However, as scaling relations show, dispersion of relaxation times does not depend on salt content in the PEO system. The relaxation peak for the imaginary part of electric modulus (M″) provides information on long-range motion of dipoles. Summarizing the results from imaginary part of impedance spectrum (Z″), tan δ (imaginary/real of permittivities) and M″ for the two systems under the discussion, PEO behaves like a mixture of chains with dipoles. There are interactions between the dipoles, but they are relaxing individually. Therefore, we see PEO-salt system as a polymer electrolyte where only a tiny fraction of added salt molecules becomes electrically active in promoting conductance. However, ENR-25-salt system behaves just as a macroscopic dipole and it can not display electrode polarization or electric relaxation because there is no mobility of individual dipoles. Hence, ENR-25-salt does not form a polymer electrolyte in the classic sense.

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12

Andreev, Pavel A. "Simultaneous dipole and quadrupole moment contribution in the Bogoliubov spectrum: Application of the non-integral Gross–Pitaevskii equation." Modern Physics Letters B 31, no. 13 (May 10, 2017): 1750152. http://dx.doi.org/10.1142/s0217984917501524.

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We present the Gross–Pitaevskii equation for Bose–Einstein condensates (BECs) possessing the electric dipole and the electric quadrupole moments in a non-integral form. These equations are coupled with the Maxwell equations. The model under consideration includes the dipole–dipole, the dipole–quadrupole, and the quadrupole–quadrupole interactions in terms of the electric field created by the dipoles and quadrupoles. We apply this model to obtain the Bogoliubov spectrum for three-dimensional BECs with a repulsive short-range interaction. We obtain an extra term in the Bogoliubov spectrum in comparison with the dipolar BECs. We show that the quadrupole–quadrupole interaction gives a positive contribution in the Bogoliubov spectrum. Hence, this spectrum is stable.

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13

Al-Marzoug, S. M. "Scattering of a discrete soliton by impurity in dipolar Bose–Einstein condensates." International Journal of Modern Physics B 28, no. 30 (December 4, 2014): 1450214. http://dx.doi.org/10.1142/s0217979214502142.

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Scattering of a discrete soliton by a single impurity in dipolar Bose–Einstein condensate is investigated numerically. The results show that the increase of the strength of dipolar interactions leads to repeated reflection, transmission and trapping regions due to energy exchange between the center of mass motion and the internal modes of the impurity. However, increasing the strength of the attractive nonlocal dipole–dipole interaction will result in different scattering windows. While the dipole–dipole interaction can significantly expand the trapping region of the system, nevertheless transmission resonances through the impurity are still observed.

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Zhou, Hong, Lynda Wilson, and Hongyun Wang. "On the Equilibria of the Extended Nematic Polymers under Elongational Flow." Abstract and Applied Analysis 2007 (2007): 1–15. http://dx.doi.org/10.1155/2007/36267.

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We classify the equilibrium solutions of the Smoluchowski equation for dipolar (extended) rigid nematic polymers under imposed elongational flow. The Smoluchowski equation couples the Maier-Saupe short-range interaction, dipole-dipole interaction, and an external elongational flow. We show that all stable equilibria of rigid, dipolar rod dispersions under imposed uniaxial elongational flow field are axisymmetric. This finding of axisymmetry significantly simplifies any procedure of obtaining experimentally observable equilibria.

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15

Voropayev, S. I., and Ya D. Afanasyev. "Two-dimensional vortex-dipole interactions in a stratified fluid." Journal of Fluid Mechanics 236 (March 1992): 665–89. http://dx.doi.org/10.1017/s0022112092001575.

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Planar motion produced when a viscous fluid is forced from an initial state of rest is studied. We consider a vortex dipole produced by the action of a point force (Cantwell 1986), and a vortex quadrupole produced by the action of two equal forces of opposite direction. We also present results from an experimental investigation into the dynamics of the interactions between vortex dipoles as well as between vortex dipoles and a vertical wall in a stratified fluid. Theoretical consideration reveals that the dynamics of two-dimensional vortex-dipole interactions are determined by two main governing parameters: the dipolar intensity of the vorticity distribution (momentum) and the quadrupolar intensity of the vorticity distribution of the flow. We document details of different basic types of interactions and present a physical interpretation of the results obtained in terms of vortex multipoles: dipoles, quadrupoles and their combinations.

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16

Rotaru, Andrei, Andrew J. Miller, Donna C. Arnold, and Finlay D. Morrison. "Towards novel multiferroic and magnetoelectric materials: dipole stability in tetragonal tungsten bronzes." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, no. 2009 (February 28, 2014): 20120451. http://dx.doi.org/10.1098/rsta.2012.0451.

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We discuss the strategy for development of novel functional materials with the tetragonal tungsten bronze structure. From the starting composition Ba 6 GaNb 9 O 30 , the effect of A- and B-site substitutions on the dielectric properties is used to develop an understanding of the origin and stability of the dipolar response in these compounds. Both tetragonal strain induced by large B-site cations and local strain variations created by isovalent A-site substitutions enhance dipole stability but result in a dilute, weakly correlated dipolar response and canonical relaxor behaviour. Decreasing cation size at the perovskite A2-site increases the dipolar displacements in the surrounding octahedra, but insufficiently to result in dipole ordering. Mechanisms introducing small A-site lanthanide cations and incorporation of A-site vacancies to induce ferroelectricity and magnetism are presented.

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17

Kashyap, Hemant K., and Ranjit Biswas. "Solvation Dynamics of Dipolar Probes in Dipolar Room Temperature Ionic Liquids: Separation of Ion−Dipole and Dipole−Dipole Interaction Contributions." Journal of Physical Chemistry B 114, no. 1 (January 14, 2010): 254–68. http://dx.doi.org/10.1021/jp906023p.

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18

BENSEGHIR, A., W. A. T. WAN ABDULLAH, B. A. UMAROV, and B. B. BAIZAKOV. "PARAMETRIC EXCITATION OF SOLITONS IN DIPOLAR BOSE–EINSTEIN CONDENSATES." Modern Physics Letters B 27, no. 25 (September 23, 2013): 1350184. http://dx.doi.org/10.1142/s0217984913501844.

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In this paper, we study the response of a Bose–Einstein condensate with strong dipole–dipole atomic interactions to periodically varying perturbation. The dynamics is governed by the Gross–Pitaevskii equation with additional nonlinear term, corresponding to a nonlocal dipolar interactions. The mathematical model, based on the variational approximation, has been developed and applied to parametric excitation of the condensate due to periodically varying coefficient of nonlocal nonlinearity. The model predicts the waveform of solitons in dipolar condensates and describes their small amplitude dynamics quite accurately. Theoretical predictions are verified by numerical simulations of the nonlocal Gross–Pitaevskii equation and good agreement between them is found. The results can lead to better understanding of the properties of ultra-cold quantum gases, such as 52 Cr , 164 Dy and 168 Er , where the long-range dipolar atomic interactions dominate the usual contact interactions.

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Russell, Hannah, Rachel Stewart, Christopher Prior, Vasily S. Oganesyan, Thembaninkosi G. Gaule, and Janet E. Lovett. "DEER and RIDME Measurements of the Nitroxide-Spin Labelled Copper-Bound Amine Oxidase Homodimer from Arthrobacter Globiformis." Applied Magnetic Resonance 52, no. 8 (March 29, 2021): 995–1015. http://dx.doi.org/10.1007/s00723-021-01321-6.

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AbstractIn the study of biological structures, pulse dipolar spectroscopy (PDS) is used to elucidate spin–spin distances at nanometre-scale by measuring dipole–dipole interactions between paramagnetic centres. The PDS methods of Double Electron Electron Resonance (DEER) and Relaxation Induced Dipolar Modulation Enhancement (RIDME) are employed, and their results compared, for the measurement of the dipolar coupling between nitroxide spin labels and copper-II (Cu(II)) paramagnetic centres within the copper amine oxidase from Arthrobacter globiformis (AGAO). The distance distribution results obtained indicate that two distinct distances can be measured, with the longer of these at c.a. 5 nm. Conditions for optimising the RIDME experiment such that it may outperform DEER for these long distances are discussed. Modelling methods are used to show that the distances obtained after data analysis are consistent with the structure of AGAO.

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Campi, C., A. Pascarella, A. Sorrentino, and M. Piana. "Highly Automated Dipole EStimation (HADES)." Computational Intelligence and Neuroscience 2011 (2011): 1–11. http://dx.doi.org/10.1155/2011/982185.

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Automatic estimation of current dipoles from biomagnetic data is still a problematic task. This is due not only to the ill-posedness of the inverse problem but also to two intrinsic difficulties introduced by the dipolar model: the unknown number of sources and the nonlinear relationship between the source locations and the data. Recently, we have developed a new Bayesian approach, particle filtering, based on dynamical tracking of the dipole constellation. Contrary to many dipole-based methods, particle filtering does not assume stationarity of the source configuration: the number of dipoles and their positions are estimated and updated dynamically during the course of the MEG sequence. We have now developed a Matlab-based graphical user interface, which allows nonexpert users to do automatic dipole estimation from MEG data with particle filtering. In the present paper, we describe the main features of the software and show the analysis of both a synthetic data set and an experimental dataset.

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Riera, Jorge J., Takeshi Ogawa, Takakuni Goto, Akira Sumiyoshi, Hiroi Nonaka, Alan Evans, Hiroyoshi Miyakawa, and Ryuta Kawashima. "Pitfalls in the dipolar model for the neocortical EEG sources." Journal of Neurophysiology 108, no. 4 (August 15, 2012): 956–75. http://dx.doi.org/10.1152/jn.00098.2011.

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For about six decades, primary current sources of the electroencephalogram (EEG) have been assumed dipolar in nature. In this study, we used electrophysiological recordings from anesthetized Wistar rats undergoing repeated whisker deflections to revise the biophysical foundations of the EEG dipolar model. In a first experiment, we performed three-dimensional recordings of extracellular potentials from a large portion of the barrel field to estimate intracortical multipolar moments generated either by single spiking neurons (i.e., pyramidal cells, PC; spiny stellate cells, SS) or by populations of them while experiencing synchronized postsynaptic potentials. As expected, backpropagating spikes along PC dendrites caused dipolar field components larger in the direction perpendicular to the cortical surface (49.7 ± 22.0 nA·mm). In agreement with the fact that SS cells have “close-field” configurations, their dipolar moment at any direction was negligible. Surprisingly, monopolar field components were detectable both at the level of single units (i.e., −11.7 ± 3.4 nA for PC) and at the mesoscopic level of mixed neuronal populations receiving extended synaptic inputs within either a cortical column (−0.44 ± 0.20 μA) or a 2.5-m3-voxel volume (−3.32 ± 1.20 μA). To evaluate the relationship between the macroscopically defined EEG equivalent dipole and the mesoscopic intracortical multipolar moments, we performed concurrent recordings of high-resolution skull EEG and laminar local field potentials. From this second experiment, we estimated the time-varying EEG equivalent dipole for the entire barrel field using either a multiple dipole fitting or a distributed type of EEG inverse solution. We demonstrated that mesoscopic multipolar components are altogether absorbed by any equivalent dipole in both types of inverse solutions. We conclude that the primary current sources of the EEG in the neocortex of rodents are not precisely represented by a single equivalent dipole and that the existence of monopolar components must be also considered at the mesoscopic level.

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Vudragović, Dušan, and Antun Balaž. "Faraday and Resonant Waves in Dipolar Cigar-Shaped Bose-Einstein Condensates." Symmetry 11, no. 9 (September 1, 2019): 1090. http://dx.doi.org/10.3390/sym11091090.

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Faraday and resonant density waves emerge in Bose-Einstein condensates as a result of harmonic driving of the system. They represent nonlinear excitations and are generated due to the interaction-induced coupling of collective oscillation modes and the existence of parametric resonances. Using a mean-field variational and a full numerical approach, we studied density waves in dipolar condensates at zero temperature, where breaking of the symmetry due to anisotropy of the dipole-dipole interaction (DDI) plays an important role. We derived variational equations of motion for the dynamics of a driven dipolar system and identify the most unstable modes that correspond to the Faraday and resonant waves. Based on this, we derived the analytical expressions for spatial periods of both types of density waves as functions of the contact and the DDI strength. We compared the obtained variational results with the results of extensive numerical simulations that solve the dipolar Gross-Pitaevskii equation in 3D, and found a very good agreement.

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Nagy, Sándor. "The frequency of the two lowest energies of interaction in dipolar hard sphere systems." Analecta Technica Szegedinensia 14, no. 2 (December 8, 2020): 13–18. http://dx.doi.org/10.14232/analecta.2020.2.13-18.

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This publication was inspired by the study of chaining in dipolar systems. Two adjacent particles form a chain is usually decided by energy or distance criterion. This prompted the author to investigate the frequency of interaction energy between nearby chain-forming particles in the dipolar system. So what is the frequency of the two lowest energies. Does have raison d’etre of the energy-based chaining criterion? Because if so, in the frequency chart qualitative change should have see at 70-75%, compared to the lowest possible energy. No such qualitative change was observed in the computer simulations. Monte Carlo simulations were performed at many densities and dipole moments in a dipolar hard sphere system. The simulation results were theoretically interpreted using the Boltzmann distribution The theoretical relationship was generalized to a wide range of density and dipole moments by fitting three suitable parameters. The fitting was necessary due to the compressive effect of density.

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Yang, Guoquan, Juan Guo, and Suying Zhang. "Influence of the dipole–dipole interaction on the interference between Bose–Einstein condensates." International Journal of Modern Physics B 33, no. 07 (March 20, 2019): 1950048. http://dx.doi.org/10.1142/s0217979219500486.

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We have investigated the interference of the dipolar Bose–Einstein condensates (DBECs) released from a double-well potential and studied the effects of dipole–dipole interaction (DDI) on the interference phenomena. We find that the DDI plays an important role in the interference process. When the effective polarization direction of the dipolar atoms is in the normal direction of the condensate plane, with the increasing of the strength of DDI, the visibility of fringes reduces and the width of fringes becomes larger. When the strength of DDI is fixed and the effective polarization direction of the dipolar atoms deviates from the normal direction of the condensate plane, the interference fringes become bent. Especially, for the situation of polarization parallel to the condensate plane, the interference fringes in the central regions become wave-shaped and vortex–antivortex pairs can be formed due to the anisotropic DDI. In addition, vortex–antivortex pairs could also be created by the spatial and temporal control of the DDI.

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Boro Saikia, S., T. Lueftinger, S. V. Jeffers, C. P. Folsom, V. See, P. Petit, S. C. Marsden, et al. "Direct evidence of a full dipole flip during the magnetic cycle of a sun-like star." Astronomy & Astrophysics 620 (December 2018): L11. http://dx.doi.org/10.1051/0004-6361/201834347.

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Context.The behaviour of the large-scale dipolar field, during a star’s magnetic cycle, can provide valuable insight into the stellar dynamo and associated magnetic field manifestations such as stellar winds.Aims.We investigate the temporal evolution of the dipolar field of the K dwarf 61 Cyg A using spectropolarimetric observations covering nearly one magnetic cycle equivalent to two chromospheric activity cycles.Methods.The large-scale magnetic field geometry is reconstructed using Zeeman Doppler imaging, a tomographic inversion technique. Additionally, the chromospheric activity is also monitored.Results.The observations provide an unprecedented sampling of the large-scale field over a single magnetic cycle of a star other than the Sun. Our results show that 61 Cyg A has a dominant dipolar geometry except at chromospheric activity maximum. The dipole axis migrates from the southern to the northern hemisphere during the magnetic cycle. It is located at higher latitudes at chromospheric activity cycle minimum and at middle latitudes during cycle maximum. The dipole is strongest at activity cycle minimum and much weaker at activity cycle maximum.Conclusions.The behaviour of the large-scale dipolar field during the magnetic cycle resembles the solar magnetic cycle. Our results are further confirmation that 61 Cyg A indeed has a large-scale magnetic geometry that is comparable to the Sun’s, despite being a slightly older and cooler K dwarf.

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Giorgini, M. G. "Raman noncoincidence effect: A spectroscopic manifestation of the intermolecular vibrational coupling in dipolar molecular liquids." Pure and Applied Chemistry 76, no. 1 (January 1, 2004): 157–69. http://dx.doi.org/10.1351/pac200476010157.

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This lecture addresses the analysis of the noncoincidence effect (NCE), a spectroscopic manifestation of the intermolecular coupling in molecular liquids. The vibrational bandshapes of molecular groups like C=O (strongly active in the IR spectrum) in dipolar liquids exhibit this phenomenon at a rather large extent. It will be shown that the vibrational exciton approach, developed under the assumption of the transition dipole coupling (TDC) mechanism, predicts how the orientational structure of the molecular liquid determines the magnitude and sign of the NCE. Specifically, it predicts that in simple molecular liquids, solely structured by dipolar forces, the NCE is large and positive, whereas when liquid structures are dominated by non-dipolar forces (as those present in H-bonded liquids), this scenario dramatically changes and IR-active modes may give rise to negative NCEs. This lecture is intended to offer a general overview of NCEs observed in dipolar (simple and structured) liquids in different thermodynamic conditions and of the theoretical and simulation results that assisted in their interpretation.

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de la Concepción, Juan García, Martín Ávalos, Pedro Cintas, José L. Jiménez, and Mark E. Light. "On the dual reactivity of a Janus-type mesoionic dipole: experiments and theoretical validation." Organic & Biomolecular Chemistry 16, no. 26 (2018): 4778–83. http://dx.doi.org/10.1039/c8ob01195h.

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Srivastava, Ankita, and Neeraj Mehta. "Enhancement of polaron-hopping-based a.c. conduction in semiconducting STS (Se–Te–Sn) glass by silver incorporation." Dalton Transactions 47, no. 30 (2018): 10187–94. http://dx.doi.org/10.1039/c8dt00717a.

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Li, Hongwei, Alexander Kamasah, and Arthur G. Suits. "Imaging H abstraction dynamics in crossed molecular beams: O(3P) + propanol isomers." Physical Chemistry Chemical Physics 21, no. 26 (2019): 14186–94. http://dx.doi.org/10.1039/c8cp06351f.

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Direct rebound dynamics are revealed for bimolecular reaction of the ground state O(³P) atom with propanol isomers, involving the post transition state long-range dipole–dipole interaction between the dipolar OH and hydroxypropyl radicals.

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30

Lim, Kyung-Geun, Soyeong Ahn, and Tae-Woo Lee. "Energy level alignment of dipolar interface layer in organic and hybrid perovskite solar cells." Journal of Materials Chemistry C 6, no. 12 (2018): 2915–24. http://dx.doi.org/10.1039/c8tc00166a.

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31

Bruno, M., and S. Ghignone. "A new computational strategy to calculate the surface energy of a dipolar crystal surface." CrystEngComm 23, no. 27 (2021): 4791–98. http://dx.doi.org/10.1039/d1ce00403d.

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32

Chavez, Patricia, William Ducker, Jacob Israelachvili, and Kathryn Maxwell. "Adsorption of Dipolar (Zwitterionic) Surfactants to Dipolar Surfaces." Langmuir 12, no. 17 (January 1996): 4111–15. http://dx.doi.org/10.1021/la950793g.

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33

Linse, Per. "Quasi-2d fluids of dipolar superballs in an external field." Soft Matter 11, no. 19 (2015): 3900–3912. http://dx.doi.org/10.1039/c5sm00338e.

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(Top) Dipolar superballs with dipole moment in 001, 011, and 111-direction and (bottom) structure in quasi-2d fluids with an external field in the horizontal direction. The degree of attraction between strings depends and the structures formed depends decisively on the direction of the dipole in the principal axis system of the superballs.

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34

Ilg, Patrick, and Siegfried Hess. "Nonequilibrium Dynamics and Magnetoviscosity of Moderately Concentrated Magnetic Liquids: A dynamic Mean-field Study." Zeitschrift für Naturforschung A 58, no. 11 (November 1, 2003): 589–600. http://dx.doi.org/10.1515/zna-2003-1101.

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A mean-field Fokker-Planck equation approach to the dynamics of ferrofluids in the presence of a magnetic field and velocity gradients is proposed that incorporates magnetic dipole-dipole interactions of the colloidal particles. The model allows to study the combined effect of a magnetic field and dipolar interactions on the viscosity of the ferrofluid. It is found that dipolar interactions lead to additional non-Newtonian contributions to the stress tensor, which modify the behavior of the non-interacting system. The predictions of the present model are in qualitative agreement with experimental results, such as the enhancement as well as the different anisotropy of the magnetoviscous effect and the dependence on the symmetric velocity gradient.

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35

Liu, Xianfeng, Lue Xiang, Jiayi Li, Ying Wu, and Ke Zhang. "Stoichiometric imbalance-promoted step-growth polymerization based on self-accelerating 1,3-dipolar cycloaddition click reactions." Polymer Chemistry 11, no. 1 (2020): 125–34. http://dx.doi.org/10.1039/c9py01362h.

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A stoichiometric imbalance-promoted step growth polymerization method was developed based on self-accelerating 1,3-dipolar cycloaddition click reactions of Sondheimer diyne and varied 1,3-dipoles, such as diazo, sydnone, and nitrone groups.

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36

Lebold, Terry P., and Michael A. Kerr. "Intramolecular annulations of donor–acceptor cyclopropanes." Pure and Applied Chemistry 82, no. 9 (June 30, 2010): 1797–812. http://dx.doi.org/10.1351/pac-con-09-09-28.

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The intramolecular reaction of donor–acceptor cyclopropanes with various dipoles and dipolar equivalents allows access to a variety of bicyclic adducts with good stereocontrol. The linkers can often be cleaved to provide stereodefined products.

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37

Velasco Fuentes, O. U., G. J. F. van Heijst, and B. E. Cremers. "Chaotic transport by dipolar vortices on a β-plane." Journal of Fluid Mechanics 291 (May 25, 1995): 139–61. http://dx.doi.org/10.1017/s0022112095002655.

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During the meandering motion of a dipolar vortex on a β-plane mass is exchanged both between the dipole and the ambient fluid and between the two dipole halves. The mass exchange (as well as the meandering motion) is caused by variations of the relative vorticity of the vortices due to conservation of potential vorticity. Previous studies have shown that a modulated point-vortex model captures the essential features in the dipole evolution. For this model we write the equations of motion of passive tracers in the form of a periodically perturbed integrable Hamiltonian system and subsequently study transport using a ‘dynamical-systems theory’ approach. The amount of mass exchanged between different regions of the flow is evaluated as a function of two parameters: the gradient of ambient vorticity, β, and the initial direction of propagation of the dipole, α0. Mass exchange between the dipole and the surroundings increases with increasing both β and α0. The exchange rate (amount of mass exchanged per unit time) increases with β and has a maximum for a particular value of α0 (≈ 0.62π). Dipolar vortices in a rotating fluid (with a sloping bottom providing the ‘topographic’ β-effect) show, in addition to the relative vorticity variations, a second perturbation that leads to exchange of mass. The points where vorticity is extreme approach each other as the dipole moves to shallower parts of the fluid and separate as the couple moves to deeper parts. This mechanism is studied independently and it is shown to lead to a stronger exchange between the dipole halves and the ambient fluid but no exchange between the two dipole halves.

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Lehmann, Frank, David E. Boerner, Klaus Holliger, and Alan G. Green. "Multicomponent georadar data: Some important implications for data acquisition and processing." GEOPHYSICS 65, no. 5 (September 2000): 1542–52. http://dx.doi.org/10.1190/1.1444842.

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Many seismic reflection processing techniques are applied routinely to ground‐penetrating radar (georadar or GPR) data. Although similarities exist between seismic (acoustic) and radar wave propagation there are some significant differences, some of the most important of which are associated with the dipole nature (1) of georadar sources and receivers and (2) of elemental sources used to represent scattering bodies. Neglecting the dipole character of electromagnetic surveys may result in incomplete or biased images of the subsurface. In an attempt to understand better the consequences of recording dipolar wavefields, we have simulated numerous multicomponent georadar data sets. These simulations are based on the weak scattering (Born) approximation, such that point heterogeneities in the subsurface can be represented by infinitesimal dipoles with moments parallel and proportional to the incident georadar wavefields. The effects of depolarization and dispersion are not included. Nevertheless, many subsurface structures can be modeled by suites of appropriately distributed infinitesimal dipoles. Georadar images of even the simplest subsurface structures are shown to depend strongly on the relative orientations and positions of the source and receiver antennas. A positive aspect of dipolar wavefields is that multicomponent georadar profiles contain information on the locations of both in‐plane and out‐of‐plane structures. Furthermore, “pseudoscalar” wavefields can be simulated from coincident georadar data sets acquired with two pairs of parallel source‐receiver antennas, one oriented perpendicular to the other. Pseudoscalar georadar data, which are characterized by low degrees of directionality, can be processed (including migration) confidently using standard seismic processing software (assuming that dispersion is not a major problem). To illustrate the advantages of multicomponent georadar data, two field examples are presented. One demonstrates the value of recording dual‐component georadar data along isolated profiles; the other shows the benefits of combining 3-D georadar data sets acquired with dual component source‐receiver antenna pairs to form pseudoscalar wavefield images.

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Bao, Weizhu, Qinglin Tang, and Yong Zhang. "Accurate and Efficient Numerical Methods for Computing Ground States and Dynamics of Dipolar Bose-Einstein Condensates via the Nonuniform FFT." Communications in Computational Physics 19, no. 5 (May 2016): 1141–66. http://dx.doi.org/10.4208/cicp.scpde14.37s.

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AbstractWe propose efficient and accurate numerical methods for computing the ground state and dynamics of the dipolar Bose-Einstein condensates utilising a newly developed dipole-dipole interaction (DDI) solver that is implemented with the non-uniform fast Fourier transform (NUFFT) algorithm. We begin with the three-dimensional (3D) Gross-Pitaevskii equation (GPE) with a DDI term and present the corresponding two-dimensional (2D) model under a strongly anisotropic confining potential. Different from existing methods, the NUFFT based DDI solver removes the singularity by adopting the spherical/polar coordinates in the Fourier space in 3D/2D, respectively, thus it can achieve spectral accuracy in space and simultaneously maintain high efficiency by making full use of FFT and NUFFT whenever it is necessary and/or needed. Then, we incorporate this solver into existing successful methods for computing the ground state and dynamics of GPE with a DDI for dipolar BEC. Extensive numerical comparisons with existing methods are carried out for computing the DDI, ground states and dynamics of the dipolar BEC. Numerical results show that our new methods outperform existing methods in terms of both accuracy and efficiency.

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Koval, Eugene A., and Oksana A. Koval. "Short-Range Interaction Impact on Two-Dimensional Dipolar Scattering." EPJ Web of Conferences 173 (2018): 06008. http://dx.doi.org/10.1051/epjconf/201817306008.

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We report numerical investigation of the short range interaction influence on the two-dimensional quantum scattering of two dipoles. The model simulates two ultracold polar molecules collisions in two spatial dimensions. The used algorithm allows us to quantitatively analyse the scattering of two polarized dipoles with account for strongly anisotropic nature of dipolar interaction. The strong dependence of the scattering total cross section on the short range interaction radius was discovered for threshold collision energies. We also discuss differences of calculated scattering cross section dependencies for different polarisation axis tilt angles.

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41

Tao, R. "Structure and Dynamics of Dipolar Fluids Under Strong Shear." International Journal of Modern Physics B 17, no. 16 (June 30, 2003): 3057–63. http://dx.doi.org/10.1142/s0217979203021800.

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Molecular dynamical simulation has been carried out to investigate the structure and dynamics of a dipolar fluid under strong shear. The dipolar fluid consists of polizable particles, which have an induced dipole moment in the applied field direction. The shear stress is perpendicular to the field direction. When the shear stress is small, the flow has a flowing-chain structure. If the shear stress increases beyond a critical value, the flowing-chain structure changes to flowing layer structure. Each layer is parallel to flow direction and the shear direction. Within one layer, the particles form strings in the flow direction.

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Zhao, Qiang. "Vortex states in rotating two-component dipolar Bose–Einstein condensates." International Journal of Modern Physics B 33, no. 10 (April 20, 2019): 1950080. http://dx.doi.org/10.1142/s0217979219500802.

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We consider the stationary state properties of pseudo-spin-1/2 rotating dipolar Bose–Einstein condensates (BECs) by numerical simulations of the Gross–Pitaevskii equation. Different vortex structures in each component are studied, depending on the competition between the dipole–dipole interactions (DDIs) and rotational. We also investigate the differences of vortex number in the two components, showing that anisotropic nature of DDIs plays a significant role in vortices formation process.

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43

Puszkarski, H., M. Krawczyk, and J. C. S. Lévy. "Purely dipolar versus dipolar-exchange modes in cylindrical nanorods." Journal of Applied Physics 101, no. 2 (January 15, 2007): 024326. http://dx.doi.org/10.1063/1.2405134.

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Yang, Si Kyung, Hyun Cheol Ahn, Seung-Joon Jeon, Inge Asselberghs, Koen Clays, André Persoons, and Bong Rae Cho. "First hyperpolarizabilities of dipolar, bis-dipolar, and octupolar molecules." Chemical Physics Letters 403, no. 1-3 (February 2005): 68–71. http://dx.doi.org/10.1016/j.cplett.2004.12.112.

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Tomé, Augusto C., Maria G. P. M. S. Neves, and José A. S. Cavaleiro. "Porphyrins and other pyrrolic macrocycles in cycloaddition reactions." Journal of Porphyrins and Phthalocyanines 13, no. 04n05 (April 2009): 408–14. http://dx.doi.org/10.1142/s1088424609000619.

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Porphyrins and other pyrrolic macrocycles can participate in a range of pericyclic reactions. This review deals mainly with their use in Diels-Alder reactions (as dienes and dienophiles) and in 1,3-dipolar cycloadditions (as 1,3-dipoles and dipolarophiles)

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Kumar, Shyambhu, and Ranjit Prasad Yadav. "Semiclassical Theory for Low Density Properties of Polar Hard D-Sphere Fluid Mixtures." Academic Voices: A Multidisciplinary Journal 5 (September 30, 2016): 48–55. http://dx.doi.org/10.3126/av.v5i0.15852.

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In the present paper, expansions are obtained for density-independent pair distribution function and second virial coefficient for D-dimensional molecular fluid mixtures of dipolar hard D-spheres in the semiclassical limit. Numerical results for the second virial coefficient are also estimated for binary mixture of (i) hard spheres and dipolar hard spheres and (ii) hard discs and dipolar hard discs. It is found that the quantum effects increase with increase of dipole moment μ2 as well as the concentration x2. The purpose of the present work is to develop a theory for calculating the low density properties of the polar hard D-sphere fluid mixture in the semiclassical limit. We have also developed the theory for estimating the quantum corrections to the density independent pair distribution function (PDF) and second virial coefficient of the polar D-sphere fluid mixtures.Academic Voices Vol.5 2015: 48-55

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47

Abelmann, Leon, Tijmen A. G. Hageman, Per A. Löthman, Massimo Mastrangeli, and Miko C. Elwenspoek. "Three-dimensional self-assembly using dipolar interaction." Science Advances 6, no. 19 (May 2020): eaba2007. http://dx.doi.org/10.1126/sciadv.aba2007.

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Interaction between dipolar forces, such as permanent magnets, generally leads to the formation of one-dimensional chains and rings. We investigated whether it was possible to let dipoles self-assemble into three-dimensional structures by encapsulating them in a shell with a specific shape. We found that the condition for self-assembly of a three-dimensional crystal is satisfied when the energies of dipoles in the parallel and antiparallel states are equal. Our experiments show that the most regular structures are formed using cylinders and cuboids and not by spheroids. This simple design rule will help the self-assembly community to realize three-dimensional crystals from objects in the micrometer range, which opens up the way toward previously unknown metamaterials.

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Wang, Huapei, Dennis V. Kent, and Pierre Rochette. "Weaker axially dipolar time-averaged paleomagnetic field based on multidomain-corrected paleointensities from Galapagos lavas." Proceedings of the National Academy of Sciences 112, no. 49 (November 23, 2015): 15036–41. http://dx.doi.org/10.1073/pnas.1505450112.

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The geomagnetic field is predominantly dipolar today, and high-fidelity paleomagnetic mean directions from all over the globe strongly support the geocentric axial dipole (GAD) hypothesis for the past few million years. However, the bulk of paleointensity data fails to coincide with the axial dipole prediction of a factor-of-2 equator-to-pole increase in mean field strength, leaving the core dynamo process an enigma. Here, we obtain a multidomain-corrected Pliocene–Pleistocene average paleointensity of 21.6 ± 11.0 µT recorded by 27 lava flows from the Galapagos Archipelago near the Equator. Our new result in conjunction with a published comprehensive study of single-domain–behaved paleointensities from Antarctica (33.4 ± 13.9 µT) that also correspond to GAD directions suggests that the overall average paleomagnetic field over the past few million years has indeed been dominantly dipolar in intensity yet only ∼60% of the present-day field strength, with a long-term average virtual axial dipole magnetic moment of the Earth of only 4.9 ± 2.4 × 1022 A⋅m2.

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Mohtat, Bita, Seyyed Amir Siadati, and Mohammad A. Khalilzadeh. "Understanding the mechanism of the 1,3-dipolar cycloaddition reaction between a thioformaldehyde S-oxide and cyclobutadiene: Competition between the stepwise and concerted routes." Progress in Reaction Kinetics and Mechanism 44, no. 3 (May 12, 2019): 213–21. http://dx.doi.org/10.1177/1468678319845863.

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Changing the mechanism of the widely used 1,3-dipolar cycloaddition reaction from its usual asynchronous one-step pattern to the rarely observed stepwise form leads to the emergence of intermediates, side products, and other impurities. Thus, it is crucial to determine the nature of the mechanism of the 1,3-dipolar cycloaddition reaction between a special 1,3-dipole and a specified dipolarophile (by theoretical methods) before using them for synthesizing a desired product. In this study, therefore, we have investigated the possibility of some probable intermediates emergence in the 1,3-dipolar cycloaddition reaction between cyclobutadiene and thioformaldehyde S-oxide. The results showed that emergence of Int (B) (−52.1 kcal mol−1) via transition state (B-1) is favorable both thermodynamically and kinetically (in comparison with all other stepwise routes). That is, developing probable impurities should not be neglected at least in the cases of the reactions between some thioformaldehyde S-oxide and some dipolarophiles.

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TOMÉ, AUGUSTO C., PAULA S. S. LACERDA, ANA M. G. SILVA, MARIA G. P. M. S. NEVES, and JOSÉ A. S. CAVALEIRO. "Synthesis of new tetrapyrrolic derivatives—porphyrins as dienophiles or dipolarophiles." Journal of Porphyrins and Phthalocyanines 04, no. 05 (August 2000): 532–37. http://dx.doi.org/10.1002/1099-1409(200008)4:5<532::aid-jpp267>3.0.co;2-0.

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Porphyrins participate as dienophiles in Diels-Alder reactions with ortho-quinodimethanes or pentacene. They can also behave as dipolarophiles in 1,3-dipolar cycloadditions with a range of 1,3-dipoles. These two reaction types were successfully used to synthesize novel chlorins, bacteriochlorins and isobacteriochlorins.

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Journal articles on the topic 'Dipolar'

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