Relevant bibliographies by topics / Dipolar

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  1. Journal articles
  2. Dissertations / Theses
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  4. Book chapters
  5. Conference papers
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Academic literature on the topic 'Dipolar'

Author: Grafiati
Published: 4 June 2021
Last updated: 9 February 2022

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Journal articles on the topic "Dipolar"

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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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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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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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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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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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Dissertations / Theses on the topic "Dipolar"

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McClenaghan, Deborah. "Chiral 1,3-dipolar cycloadditions." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367695.

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Sutcliffe, Oliver Brook. "New extended dipolar systems." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366511.

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Piccin, Rafael. "Interações magnéticas dipolares entre fios e microfios magnéticos." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278210.

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Orientador: Marcelo Knobel
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Nesta dissertação de mestrado são apresentados resultados do efeito do campo dipolar magnético em conjuntos formados por fios e microfios ferromagnéticos amorfos de composição Fe77,5Sil2,5B15. Devido à estrutura de domínios peculiar destes fios magnéticos, eles podem ser, em princípio, aproximados a dipolos magnéticos, permitido a análise destes campos magnetostáticos nestas estruturas macroscópicas. Os estudos foram realizados em conjuntos de fios colocados lado a lado. As curvas de magnetização foram medidas variando-se o número de elementos. Além disso, no caso de dois fios, medidas em função da separação entre os dois elementos foram realizadas. Estas medidas magnéticas foram feitas empregando um magnetômetro desenvolvido durante o projeto e também utilizado um magnetômetro SQUID. Os resultados são explicados considerando o campo dipolar gerado por cada fio do conjunto, que altera os valores do campo de inversão da magnetização e faz com que platôs sejam observados nas curvas de magnetização. Os efeitos do campo dipolar também foram observados em medidas de magnetoimpedância, onde a presença do fio rico em Fe desloca as curvas de magnetoimpedância de um fio amorfo base Co, de modo análogo a um campo bias
Abstract: The results of the magnetic dipolar field in an array of amorphous ferromagnetic wires and microwires of composition Fe77,5Si12,5B15 are presented in this dissertation. Due to their peculiar domain structure, in principle, they can be approximated to magnetic dipoles, a11owing the analysis of the magnetostatic field among these macroscopic entities. The studies were carried out in arrays of wires placed side by side. The magnetic loops were measured changing the number of elements. Moreover, in the case of two parallel wires, measurements as function of the distance between the wires were performed. The magnetic measurements were carried out in an inductive magnetometer developed during this project and a1so using a SQUID magnetometer. The results are explained considering the dipolar field created by each wire in the array. The dipolar field changes the reversal field of the wires, a11owing the appearance of plateaus during the demagnetization. The effects of the dipolar field were also observed in magnetoimpedance measurements when a Fe-rich wire in placed near an amorphous Co-based wire, its presence dislocates the Co-based wire magnetoimpedance curves, ana1ogously as a bias field
Mestrado
Física
Mestre em Física
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Yi, Su. "Properties of trapped dipolar condensates." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/27356.

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Wragg, M. J. "Critical properties of dipolar ferromagnetics." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235076.

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Spiteri, Ludovic. "Self-assembly of dipolar particles." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0261/document.

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Cette thèse couvre l'auto-assemblage de particules dipolaires (magnétiques/électriques). Ces systèmes sont abondants en physique de la matière condensée (molécules et nanoparticules magnétiques, particules colloïdales magnétiques, bactérie magnétotactique, etc.). Sur un plan fondamental, ils représentent un défi important en raison de l'anisotropie et de la longue portée de l'interaction de paire. Le principal objectif de ce travail de recherche est de prédire les microstructures de ces systèmes en tenant compte de façon adéquate de l'interaction complexe dipôle-dipôle ainsi que des effets stériques et ceux dus à un éventuel confinement. Comprendre et revisiter les interactions de filaments dipolaires tels que des aiguilles et des chaînes faites de billes dipolaires est une première étape importante de cette thèse. En effet, les chaînes sont les constituants élémentaires de nombreux systèmes dipolaires, notamment sous l'effet d'un champ magnétique extérieur appliqué. Ensuite, l'agrégation colonnaire des chaînes dipolaires est examinée, ce qui conduit aussi naturellement à l'étude des cristaux dipolaires massifs où une nouvelle phase est découverte. Le cas plus générique des chaînes hélicoïdales est discuté en considérant les situations limites que sont les chaînes linéaires droites et en zigzag. L'association des chaînes dipolaires, dans le cas bidimensionnel, forme des rubans, puis une monocouche avec un réseau hexagonal. La réponse non triviale d'un tel réseau à un champ magnétique perpendiculaire imposé est aussi étudiée. Il est démontré qu'un réseau rhombique peut être induit de cette façon. Finalement, la sédimentation de particules paramagnétiques dans une monocouche inclinée en présence d'un champ magnétique est explorée via une étude mêlant expériences, théorie et simulations. L'ordre induit par gravité s'avère être une voie prometteuse pour l'élaboration contrôlée de réseaux bidimensionnels
This thesis covers the self-assembly of dipolar (magnetic/dielectric) particles. These systems are abundant in condensed matter physics (magnetic molecules and nanoparticles, magnetic colloidal particles, magnetotactic bacteria, etc). They also represent a fundamental challenge owing to the both long range and anisotropic nature of the pair interaction. The main objective of this research work is to predict the microstructures of these systems by properly handling the intricate dipole-dipole interaction combined with steric and possibly confinement effects. Understanding and revisiting the interaction of dipolar filaments such as needles or chains made up of dipolar beads is a first important achievement in this thesis. Indeed, the chains are the fundamental building blocks of many dipolar systems especially under applied external magnetic field. Then, the columnar aggregation of dipolar chains is investigated which naturally leads to the study of the bulk dipolar crystals. A new phase is discovered there. The more generic case of helical chains is discussed by considering limiting situations such as straight linear chains and zigzag chains. The association of dipolar chains in two-dimensions forms ribbons then a monolayer with triangular lattice symmetry. The interesting response of such a layer to an imposed perpendicular magnetic is addressed as well. It is demonstrated that rhombicity can be induced that way. Finally, sedimenting paramagnetic particles in a tilted monolayer in presence of a magnetic field are investigated by experiments, theory and simulations. The gravity-mediated ordering is found to be a promising route to elaborate tailored two-dimensional patterns
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Weizenmann, Antonio. "Acoplamento dipolar entre partículas ferromagnéticas." reponame:Repositório Institucional da UFSC, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/94706.

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Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-graduação em Física, Florianópolis, 2010
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Nesta Tese estudamos o efeito do acoplamento dipolar nas propriedades magnéticas de dois tipos de sistemas. O primeiro deles consiste de duas pequenas partículas cujos spins estão acoplados ferromagneticamente. Cada partícula é descrita por uma estrutura bidimensional finita de spins interagindo através da hamiltoniana de Ising, ou por uma rede finita em duas ou três dimensões de spins interagindo através da hamiltoniana de Heisenberg com spins clássicos. Em ambas as situações temos um spin central rodeado por um número variável de camadas magnéticas. O acoplamento entre spins dentro de cada partícula é ferromagnético, e consideramos uma interação dipolar apenas entre as partículas. Nós investigamos o sistema bidimensional de spins de Ising através da aproximação de campo médio e simulações de Monte Carlo. A interação dipolar é calculada de duas maneiras diferentes. Em uma delas, assumimos que a interação dipolar ocorra entre momentos magnéticos efetivos localizados nos centros das partículas, e na outra, computamos diretamente as interações entre todos os pares de spins, um em cada partícula. Mostramos que a diferença entre os valores da energia dipolar calculada pelos dois métodos é descrita por uma lei de potência do tipo d5, onde d é a distância entre os centros das partículas. Calculamos a magnetização e a susceptibilidade em função da temperatura, do número de camadas e da distância entre os centros de partículas. Mostramos que a temperatura crítica aumenta com o número de spins em cada partícula, e isso é mais notável nos cálculos realizados através da aproximação de campo médio que nas simulações de Monte Carlo. O segundo problema estudado nesta Tese consiste de um conjunto de partículas de monodomínio. Este sistema é investigado através de simulações de Monte Carlo em três redes diferentes. Consideramos uma rede cúbica simples, uma rede cúbica de face centrada e uma estrutura tipo líquido. As partículas são acoplados pela interação dipolar de longo alcance e apresentam uma anisotropia uniaxial, cuja magnitude é escolhida a partir de uma distribuição de Gauss e cujos eixos de fácil magnetização estão orientados aleatoriamente no espaço tridimensional. Determinamos a temperatura de bloqueio e as curvas de histerese em função da razão entre as magnitudes da interação dipolar e da anisotropia uniaxial. Mostramos que a remanência e o campo coercivo dependem fortemente da estrutura considerada. Estes resultados são comparados com aqueles obtidos para um sistema de partículas não interagentes.
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Trefzger, Christian. "Ultracold dipolar gases in optical lattices." Doctoral thesis, Universitat Politècnica de Catalunya, 2010. http://hdl.handle.net/10803/6596.

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Esta tesis es un trabajo teórico, en el que estudiamos la física de los átomos dipolares bosónicos ultrafríos en retículos ópticos. Éstos gases consisten de átomos o moléculas bosónicas, enfriados bajo la temperatura de degeneración cuántica, típicamente del orden de nK. En éstas condiciones, en una trampa armónica tridimensional (3D), los bosones que interaccionan débilmente condensan y forman un Condensado de Bose Einstein (BEC). Cuando se carga un BEC en un retículo óptico producido por ondas estacionarias de luz láser, se producen nuevos fenómenos físicos. Estos sistemas entonces realizan modelos de tipo Hubbard y pueden ser llevados a regimenes fuertemente correlacionados.

En 1989, M. Fisher et. al. predecían que el modelo de Bose-Hubbard homogéneo (BH) presenta la transición de fase cuántica Superfluid-Mott insulator (SF-MI). En 2002, la transición entre éstas dos fases fue observada experimentalmente por primera vez en el grupo de T. Esslinger e I. Bloch. La realización experimental de un BEC dipolar de cromo en el grupo de T. Pfau, y los progresos recientes en las técnicas de enfriamiento y atrapamiento de moléculas dipolares en los grupos de D. Jin e J. Ye, han abierto el camino hacia los gases cuánticos ultra-fríos dominados por la interacción dipolar. La evolución natural, y el reto de hoy en día por parte experimental, es de cargar BEC dipolares en retículos ópticos y estudiar los gases dipolares fuertemente correlacionados.

Antes de éste trabajo de doctorado, estudios sobre modelos de BH con interacciones extendidas a los primeros vecinos mostraron la evidencia de nuevas fases cuánticas, como el supersólido (SS) y la fase checkerboard (CB). Debido al carácter de largo alcance de la interacción dipolo-dipolo, que decae con la potencia cúbica inversa de la distancia, es necesario incluir más de un primer vecino para obtener una descripción fiel y cuantitativa de los sistemas dipolares. De hecho, al incluir más vecinos se permiten y se estabilizan aún más nuevas fases.

En esta tesis estudiamos modelos de BH con interacciones dipolares, investigando más allá del estado fundamental. Estudiamos un retículo bidimensional (2D) donde los dipolos están polarizados en dirección perpendicular al plano 2D, dando lugar a una interacción dipolar repulsiva e isotrópica. Utilizamos aproximaciones de campo-medio y un ansatz Gutzwiller, que son suficientemente correctos y adecuados para describir este sistema. Encontramos que los gases dipolares en 2D presentan una multitud de estados metaestables de tipo MI, que compiten con el estado fundamental, de modo parecido a sistemas desordenados. Estudiamos en detalle el destino de estos estados metaestables: como pueden ser preparados de manera controlada, como pueden ser detectados, cual es su tiempo de vida debido al tunnelling, y cual es su rol en los procesos de enfriamiento. Además, encontramos que el estado fundamental está caracterizado por estados MI de tipo checkerboard con coeficiente de ocupación n fraccionario (numero medio de partículas por sitio) que depende del cut-off utilizado en el radio de alcance de la interacción. Confirmamos esta predicción estudiando el mismo sistema con métodos Quantum Monte Carlo (worm algorithm). En este caso no utilizamos ningún cut-off en el radio de alcance de la interacción, y encontramos pruebas de una "Devil's staircase" en el estado fundamental, i.e. donde las fases MI aparecen en todos los n racionales del retículo subyacente. Encontramos además, regiones de los parámetros donde el estado fundamental es supersólido, obtenido drogando los sólidos con partículas o con agujeros.

En este trabajo, investigamos también como cambia la estructura precedente en 3D. Nos focalizamos en el retículo 3D más sencillo compuesto de dos planos 2D, en el cual los dipolos están polarizados perpendicularmente a los planos; la interacción dipolar es entonces repulsiva por partículas del mismo plano, mientras es atractiva por partículas en el mismo sitio de dos planos diferentes. En cambio suprimimos el tunnelling entre los planos, lo cual hace el sistema equivalente a una mezcla bosónica en un retículo 2D. Nuestros cálculos muestran que las partículas se juntan en parejas, y demostramos la existencia de la nueva fase cuántica Pair Super Solid (PSS).

Actualmente estamos estudiando un retículo 2D donde los dipolos están libres de apuntar en ambas direcciones perpendicularmente al plano, lo cual resulta en una interacción a primeros vecinos repulsiva (atractiva) por dipolos alineados (anti-alineados). Encontramos regiones de parámetros donde el estado fundamental es ferromagnético u anti-ferromagnético, y encontramos pruebas de la existencia de la fase cuántica Counterflow Super Solid (CSS).
Las nuestras predicciones tienen directas consecuencias experimentales, y esperamos que vengan pronto controladas en experimentos con gases dipolares atómicos y moleculares ultra-fríos.
This thesis is a theoretical work, in which we study the physics of ultra-cold dipolar bosonic gases in optical lattices. Such gases consist of bosonic atoms or molecules, cooled below the quantum degeneracy temperature, typically in the nK range. In such conditions, in a three-dimensional (3D) harmonic trap, weakly interacting bosons condense and form a Bose-Einstein Condensate (BEC). When a BEC is loaded into an optical lattice produced by standing waves of laser light, new kinds of physical phenomena occur.

These systems realize then Hubbard-type models and can be brought to a strongly correlated regime. In 1989, M. Fisher et. al. predicted that the homogeneous Bose-Hubbard model (BH) exhibits the Superfluid-Mott insulator (SF-MI) quantum phase transition. In 2002 the transition between these two phases were observed experimentally for the first time in the group of T. Esslinger and I. Bloch. The experimental realisation of a dipolar BEC of Chromium by the group of T. Pfau, and the recent progresses in trapping and cooling of dipolar molecules by the groups of D. Jin and J. Ye, have opened the path towards ultra-cold quantum gases with dominant dipole interactions. A natural evolution and present challenge, on the experimental side is then to load dipolar BECs into optical lattices and study strongly correlated ultracold dipolar lattice gases.

Before this PhD work, studies of BH models with interactions extended to nearest neighbours had pointed out that novel quantum phases, like supersolid (SS) and checkerboard phases (CB) are expected. Due to the long-range character of the dipole-dipole interaction, which decays as the inverse cubic power of the distance, it is necessary to include more than one nearest neighbour to have a faithful quantitative description of dipolar systems. In fact, longer-range interactions tend to allow for and stabilize more novel phases.

In this thesis we study BH models with dipolar interactions, going beyond the ground state search. We consider a two-dimensional (2D) lattice where the dipoles are polarized perpendicularly to the 2D plane, resulting in an isotropic repulsive interaction. We use the mean-field approximations and a Gutzwiller ansatz which are quite accurate and suitable to describe this system. We find that dipolar bosonic gas in 2D exhibits a multitude of insulating metastable states, often competing with the ground state, similarly as in a disordered system. We study in detail the fate of these metastable states: how can they be prepared on demand, how they can be detected, what is their lifetime due to tunnelling, and what is their role in various cooling schemes. Moreover, we find that the ground state is characterized by insulating checkerboard-like states with fractional filling factors v(average number of particles per site) that depend on the cut-off used for the interaction range. We confirm this prediction by studying the same system with Quantum Monte Carlo methods (the worm algorithm). In this case no cut-off is used, and we find evidence for a Devil's staircase in the ground state, i.e. where insulating phases appear at all rational of the underlying lattice. We also find regions of parameters where the ground state is a supersolid, obtained by doping the solids either with particles or vacancies.

In this work, we also investigate how the previous scenario changes in 3D. We focus on the simplest 3D lattice composed of two 2D layers in which the dipoles are polarized perpendicularly to the planes; the dipolar interaction is then repulsive for particles laying on the same plane, while it is attractive for particles at the same lattice site on different layers. Instead we consider inter-layer tunnelling to be suppressed, which makes the system analogous to a bosonic mixture in a 2D lattice. Our calculations show that particles pair into composites, and demonstrate the existence of the novel Pair Super Solid (PSS) quantum phase.
Currently we are studying a 2D lattice where the dipoles are free to point in both directions perpendicularly to the plane, which results in a nearest neighbour repulsive (attractive) interaction for aligned (antialigned) dipoles. We find regions of parameters where the ground state is ferromagnetic or antiferromagnetic, and find evidences for the existence of a Counterflow Super Solid (CSS) quantum phase.
Our predictions have direct experimental consequences, and we hope that they will be soon checked in experiments with ultracold dipolar atomic and molecular gases.
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9

Jackson, P. "Dipolar coupling in solid-state NMR." Thesis, Durham University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379058.

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Newell, Catherine A. "INELASTIC COLLISIONS IN COLD DIPOLAR GASES." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/30.

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Abstract:
Inelastic collisions between dipolar molecules, assumed to be trapped in a static electric field at cold (> 10−3K) temperatures, are investigated and compared with elastic collisions. For molecules with a Λ-doublet energy-level structure, a dipole moment arises because of the existence of two nearly degenerate states of opposite parity, and the collision of two such dipoles can be solved entirely analytically in the energy range of interest. Cross sections and rate constants are found to satisfy simple, universal formulas. In contrast, for molecules in a Σ electronic ground state, the static electric field induces a dipole moment in one of three rotational sublevels. Collisions between two rotor dipoles are calculated numerically; the results scale simply with molecule mass, rotational constant, dipole moment, and field strength. It might be expected that any particles interacting only under the influence of the dipole-dipole interaction would show similar behavior; however, the most important and general result of this research is that at cold temperatures inelastic rate constants and cross sections for dipoles depend strongly upon the internal structure of the molecules. The most prominent difference between the Λ-doublet and rotor molecules is variation of the inelastic cross section with applied field strength. For Λ-doublet dipoles, cross sections decrease with increasing field strength. For rotor dipoles, cross sections increase proportionally with the square of field strength. Furthermore, the rate constants of the two types of molecules depend very differently on the angular orientations of the dipoles in the electric field.
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Books on the topic "Dipolar"

1

Basel, Bettina. Dipolar Correlation Spectroscopy. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-09191-0.

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Weller, David John. Steric acceleration of intramolecular 1,3-dipolar cycloadditions. Uxbridge: Brunel University, 1993.

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Booth, Ceri. Recognition-induced acceleration of a 1,3-dipolar cycloaddition. Birmingham: University of Birmingham, 1999.

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Izutsu, Kosuke. Acid-base dissociation constants in dipolar aprotic solvents. Oxford: Blackwell Scientific Publications, 1990.

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Marchisio, Mario. Deep dipolar soundings in geothermal areas of Sardinia: Logudoro and Campidano. Luxembourg: Commission of the European Communities, 1986.

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Synthetic applications of 1,3-dipolar cycloaddition chemistry toward heterocycles and natural products. Hoboken, NJ: Wiley, 2003.

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Padwa, Albert, and William H. Pearson, eds. Synthetic Applications of 1,3-Dipolar Cycloaddition Chemistry Toward Heterocycles and Natural Products. New York, USA: John Wiley & Sons, Inc., 2002. http://dx.doi.org/10.1002/0471221902.

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Sinclair, Andrew Jamieson. Using non-covalent interaction to accelerate a [three plus two] dipolar cycloaddition reaction. Birmingham: University of Birmingham, 2000.

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Evans, D. R. Non-dipolar magnetic field models and patterns of radio emission: Uranus and Neptune compared : final report. [Washington, DC: National Aeronautics and Space Administration, 1994.

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Paul Petrus Maria de Lange. Synthesis and 1,3-dipolar reactivity of Fe(CO)3-n[subscript](CNR)n[subscript]([alpha]-diimine) complexes (n=1,3). [Amsterdam]: Universiteit van Amsterdam, 1992.

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Book chapters on the topic "Dipolar"

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Nielsen, Niels Chr, Lasse A. Strassø, and Anders B. Nielsen. "Dipolar Recoupling." In Topics in Current Chemistry, 1–45. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/128_2011_129.

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Basel, Bettina. "A General Introduction." In Dipolar Correlation Spectroscopy, 1–6. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-09191-0_1.

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Basel, Bettina. "Theory." In Dipolar Correlation Spectroscopy, 7–38. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-09191-0_2.

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Basel, Bettina. "Scope of the Thesis." In Dipolar Correlation Spectroscopy, 39–41. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-09191-0_3.

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Basel, Bettina. "Materials and Methods." In Dipolar Correlation Spectroscopy, 43–50. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-09191-0_4.

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Basel, Bettina. "Results and Discussion." In Dipolar Correlation Spectroscopy, 51–89. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-09191-0_5.

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Basel, Bettina. "Summary and Outlook." In Dipolar Correlation Spectroscopy, 91–92. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-09191-0_6.

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Tjandra, Nico. "Residual Dipolar Coupling." In Encyclopedia of Biophysics, 2213–21. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-16712-6_311.

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Nezlin, Mikhail V., and Evgenii N. Snezhkin. "Dipolar Rossby Vortices." In Springer Series in Nonlinear Dynamics, 165–75. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-88122-0_11.

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Jozef, Kowalewski, and Mler Lena. "Relaxation through Dipolar Interactions." In Nuclear Spin Relaxation in Liquids, 31–50. Second edition. | Boca Raton, FL : CRC Press, Taylor & Francis Group, [2018]: CRC Press, 2017. http://dx.doi.org/10.1201/9781351264600-3.

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Conference papers on the topic "Dipolar"

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Elbahri, M., M. K. Hedayati, and M. Abdelaziz. "Active organic dipolar antenna." In 2016 10th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (METAMATERIALS). IEEE, 2016. http://dx.doi.org/10.1109/metamaterials.2016.7746473.

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MENOTTI, CHIARA, and MACIEJ LEWENSTEIN. "ULTRA-COLD DIPOLAR GASES." In Proceedings of the 14th International Conference. WORLD SCIENTIFIC, 2008. http://dx.doi.org/10.1142/9789812779885_0010.

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Yaghjian, Arthur D. "Nonnegative energy for dipolar continua." In 2016 URSI International Symposium on Electromagnetic Theory (EMTS). IEEE, 2016. http://dx.doi.org/10.1109/ursi-emts.2016.7571358.

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LAHAYE, T., J. METZ, T. KOCH, B. FRÖHLICH, A. GRIESMAIER, and T. PFAU. "A PURELY DIPOLAR QUANTUM GAS." In Proceedings of the XXI International Conference on Atomic Physics. WORLD SCIENTIFIC, 2009. http://dx.doi.org/10.1142/9789814273008_0016.

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Gao, Tong. "Constructing Crystalline Molecular Dipolar Rotor Arrays with Ultra-Large Dipole Moments." In ICBBB '21: 2021 11th International Conference on Bioscience, Biochemistry and Bioinformatics. New York, NY, USA: ACM, 2021. http://dx.doi.org/10.1145/3448340.3448352.

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Korats, Gundars, Radu Ranta, Steven Le Cam, and Valerie Louis-Dorr. "Dipolar estimates of the cortical map." In 2014 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC). IEEE, 2014. http://dx.doi.org/10.1109/embc.2014.6943792.

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Pulido-Mancera, Laura, Mohammadreza F. Imani, and David R. Smith. "Dipolar Model for Metamaterial Imaging Systems." In 2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting. IEEE, 2018. http://dx.doi.org/10.1109/apusncursinrsm.2018.8608502.

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Moorey, Charles L., William Holderbaum, and Ben Potter. "Radiative power transmission from dipolar sources." In 2013 IEEE Wireless Power Transfer Conference (WPTC). IEEE, 2013. http://dx.doi.org/10.1109/wpt.2013.6556919.

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Verpoort, S., A. Draude, H. Franke, and R. A. Lessard. "Electrostatic patterning with organic dipolar molecules." In Photonics North 2006, edited by Pierre Mathieu. SPIE, 2006. http://dx.doi.org/10.1117/12.707952.

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Vicencio, Rodrigo A. "Flat band and dipolar discrete optics." In 2016 Progress in Electromagnetic Research Symposium (PIERS). IEEE, 2016. http://dx.doi.org/10.1109/piers.2016.7735249.

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Reports on the topic "Dipolar"

1

Carr, Lincoln D. Complex Dipolar Matter. Fort Belvoir, VA: Defense Technical Information Center, November 2014. http://dx.doi.org/10.21236/ada615453.

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Hammerberg, J. E., B. L. Holian, M. S. Murillo, and D. Winske. Molecular dynamics simulations of dipolar dusty plasmas. Office of Scientific and Technical Information (OSTI), December 1998. http://dx.doi.org/10.2172/307953.

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Cunningham, Gregory Scott. Radial diffusion in non-dipolar background fields. Office of Scientific and Technical Information (OSTI), October 2016. http://dx.doi.org/10.2172/1330624.

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Wright, Thomas W., and Romesh C. Batra. Adiabatic Shear Bands in Simple and Dipolar Plastic Materials. Fort Belvoir, VA: Defense Technical Information Center, March 1987. http://dx.doi.org/10.21236/ada182034.

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Batra, Romesh C. Adiabatic Shear Bands in Simple and Dipolar Viscoplastic Materials. Fort Belvoir, VA: Defense Technical Information Center, August 1991. http://dx.doi.org/10.21236/ada246055.

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Harvey, Jacob. Molecule Origins of Dipolar Character in Excited Electronic States. Office of Scientific and Technical Information (OSTI), September 2020. http://dx.doi.org/10.2172/1670520.

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Wu, Congjun. Unconventional States of Matter with Cold Atoms and Dipolar Molecules. Fort Belvoir, VA: Defense Technical Information Center, August 2014. http://dx.doi.org/10.21236/ada609971.

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Sears, J. Coal extraction by aprotic dipolar solvents. Final report. [Tetramethylurea, hexa-methylphosphoramide]. Office of Scientific and Technical Information (OSTI), December 1985. http://dx.doi.org/10.2172/6071145.

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Urban, Jeffry Todd. Nuclear magnetic resonance studies of quadrupolar nuclei and dipolar field effects. Office of Scientific and Technical Information (OSTI), January 2004. http://dx.doi.org/10.2172/836811.

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Goodson, T., Wang III, and C. H. Dipolar Reorientation of a Nonlinear Optical Chromophore Doped in Amorphous Polymers Investigated by Electrochromism. Fort Belvoir, VA: Defense Technical Information Center, April 1996. http://dx.doi.org/10.21236/ada307790.

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