Multipole Structure Research Articles

Is US Primacy Durable in an Asian Century?

Two issues are addressed. Is a shift from U.S. primacy to a multipolar global power structure likely? If so, is it likely to be peaceful or conflictual? Discontinuities could disrupt linear trends but by 2050, China, the US, the European Union, and India are likely to be the four largest economies. Asian integration will reinforce Asia's increasing global economic share, suggesting the prospect of an Asian century from the mid-21st century, ending U.S. economic primacy. U.S. military primacy is massive and more durable than U.S. economic primacy, but the power conferred by it is limited in scope. A peaceful power shift is most likely because of four mutually reinforcing factors. Firstly, nuclear deterrence makes the consequences of major power conflict catastrophic, so political solutions are the only viable modes of dispute resolution. Secondly, complex interdependence based on economic integration confers major benefits from peaceful commerce. Thirdly, norms and practices in East Asia over three decades of peace are reinforced by East Asian Summits and other forums for peaceful dispute resolution, confidence building, and security cooperation. Fourthly, human agency is inherently unpredictable, but a gradual power shift need not involve existential conflict over vital Chinese, EU, Indian or U.S. interests.

Recent Advances on Solar Global Magnetism and Variability

We discuss recent observational, theoretical and numerical progress made in understanding the solar global magnetism and its short and long term variability. We discuss the physical process thought to be at the origin of the solar magnetic field and its 22-yr cycle, namely dynamo action, and the nonlinear interplay between convection, rotation, radiation and magnetic field, yielding modulations of the solar constant or of the large scale flows such as the torsional oscillations. We also discuss the role of the field parity and dynamo families in explaining the complex multipolar structure of the solar global magnetic field. We then present some key MHD processes acting in the deep radiative interior and discuss the probable topology of a primordial field there. Finally we summarize how helioseismology has contributed to these recent advances and how it could contribute to resolving current unsolved problems in solar global dynamics and magnetism.

Radmis, a Novel Mitotic Spindle Protein that Functions in Cell Division of Neural Progenitors

Developmental dynamics of neural stem/progenitor cells (NSPCs) are crucial for embryonic and adult neurogenesis, but its regulatory factors are not fully understood. By differential subtractive screening with NSPCs versus their differentiated progenies, we identified the radmis (radial fiber and mitotic spindle)/ckap2l gene, a novel microtubule-associated protein (MAP) enriched in NSPCs. Radmis is a putative substrate for the E3-ubiquitin ligase, anaphase promoting complex/cyclosome (APC/C), and is degraded via the KEN box. Radmis was highly expressed in regions of active neurogenesis throughout life, and its distribution was dynamically regulated during NSPC division. In embryonic and perinatal brains, radmis localized to bipolar mitotic spindles and radial fibers (basal processes) of dividing NSPCs. As central nervous system development proceeded, radmis expression was lost in most brain regions, except for several neurogenic regions. In adult brain, radmis expression persisted in the mitotic spindles of both slowly-dividing stem cells and rapid amplifying progenitors. Overexpression of radmis in vitro induced hyper-stabilization of microtubules, severe defects in mitotic spindle formation, and mitotic arrest. In vivo gain-of-function using in utero electroporation revealed that radmis directed a reduction in NSPC proliferation and a concomitant increase in cell cycle exit, causing a reduction in the Tbr2-positive basal progenitor population and shrinkage of the embryonic subventricular zone. Besides, radmis loss-of-function by shRNAs induced the multipolar mitotic spindle structure, accompanied with the catastrophe of chromosome segregation including the long chromosome bridge between two separating daughter nuclei. These findings uncover the indispensable role of radmis in mitotic spindle formation and cell-cycle progression of NSPCs.

Perspective: Coulomb fluids—Weak coupling, strong coupling, in between and beyond

We present a personal view on the current state of statistical mechanics of Coulomb fluids with special emphasis on the interactions between macromolecular surfaces, concentrating on the weak and the strong coupling limits. Both are introduced for a (primitive) counterion-only system in the presence of macroscopic, uniformly charged boundaries, where they can be derived systematically. Later we show how this formalism can be generalized to the cases with additional characteristic length scales that introduce new coupling parameters into the problem. These cases most notably include asymmetric ionic mixtures with mono- and multivalent ions that couple differently to charged surfaces, ions with internal charge (multipolar) structure and finite static polarizability, where weak and strong coupling limits can be constructed by analogy with the counterion-only case and lead to important new insights into their properties that cannot be derived by any other means.

Geodesics in the linearized multipole solution: Distinguishing black holes from naked singularities

We analyze the behavior of the geodesic motion of test particles in the spacetime of a specific class of axially symmetric static vacuum solutions to the Einstein equations, hereafter referred to as the linearized multipole solution. We discuss its suitability to describe a quasispherical spacetime. The existence of an innermost stable circular orbit very close to the (singular) horizon of the source is established. The existence of such a stable orbit, closer than that of the Schwarzschild metric, as well as the appearance of a splitting in the admissible region of circular orbits, is shown to be due to the multipole structure of the solution, thereby providing additional potential observational evidence for distinguishing Schwarzschild black holes from naked singularities.

Structure analysis of the generalized correlator of quark and gluon for a spin-1/2 target

Abstract We analyze the structure of generalized off-diagonal and transverse-momentum dependent quark-quark and gluon-gluon correlators for a spin-1/2 hadron. Using the light-front formalism, we provide a parametrization in terms of the parton generalized transverse-momentum dependent distributions that emphasizes the multipole structure of the correlator. The results for the quark-quark correlation functions are consistent with an alternative parametrization given in terms of Lorentz covariant structures. The parametrization for the gluon-gluon generalized correlator is presented for the first time and allows one to introduce new correlation functions which can be relevant for phenomenological applications.

Thermal analysis of the Mirnov coils of Wendelstein 7-X

Mirnov coils are used to measure fluctuations of the magnetic field which are in particular generated by magnetohydrodynamic (MHD) modes. The underlying plasma currents have a multipolar structure in a poloidal cross-section. Therefore the amplitude of the magnetic fluctuations decays quickly with increasing distance from the plasma edge. It is hence important to place the Mirnov coils as close to the plasma edge as possible where they are exposed to high thermal loads. Two types of Mirnov coils are proposed to be used in Wendelstein 7-X (W7-X). Type 1 (44 Mirnov coils) should be mounted on the plasma side of wall protection panels with a graphite cap to shield them from direct plasma exposure. Type 2 (137 Mirnov coils) will be located behind the tiles of the heat shields. An important issue concerning the design of these Mirnov coils is to verify their suitability for steady state operation from the thermal point of view. Both steady state and transient finite element thermal analyses were performed for the Mirnov coils under different conditions and with different designs. The paper presents detailed thermal analyses of the Mirnov coils.

Optical Properties of a Particle above a Dielectric Interface: Cross Sections, Benchmark Calculations, and Analysis of the Intrinsic Substrate Effects

We show that the optical properties of a particle above a plane dielectric interface differ dramatically from those of the same particle embedded in a homogeneous matrix. Calculations for gold and silver spheres have been carried out in using the exact multipole expansion method, providing thus benchmark results for testing the accuracy of the available numerical methods. For silver spheres, the dependence of the extinction cross-section has been studied in detail as a function of the parameters characterizing the particle/interface system, namely, the radius of the sphere, the particle-surface distance, and the dielectric index of the substrate, as well as those characterizing the light excitation, that is, the angle of incidence and the polarization. Throughout this study we have separated the effects arising from the inhomogeneity of the applied field (interference between the incoming and reflected plane waves) from the intrinsic substrate effects resulting from the interaction with the induced surface charges on the surface. These last effects are, in the present formalism, encoded in the reflected scattered field impinging on the particle. For particles close to the interface, a rich multipolar plasmonic structure is observed, which can be described in the frame of a hybridization scheme similar to that developed for dealing with layered particles or dimers. Comparison with approximate models is also provided.

Dynamics of quadrupolar bodies in a Schwarzschild spacetime

The dynamics of extended bodies endowed with multipolar structure up to the mass quadrupole moment is investigated in the Schwarzschild background according to Dixon's model, extending previous works. The whole set of evolution equations is numerically integrated under the simplifying assumptions of constant frame components of the quadrupole tensor and that the motion of the center of mass be confined on the equatorial plane, the spin vector being orthogonal to it. The equations of motion are also solved analytically in the limit of small values of the characteristic length scales associated with the spin and quadrupole with respect to the background curvature characteristic length. The results are qualitatively and quantitatively different from previous analyses involving only spin structures. In particular, the presence of the quadrupole turns out to be responsible for the onset of a nonzero spin angular momentum, even if initially absent.

Verification of the fitted crystal‐field Hamiltonian parametrization by the crystal‐field splitting second moment

AbstractA physically valid parametrization of the crystal‐field (CF) Hamiltonian HCF has to reproduce not only the energy of Stark sublevels but also the multipolar structure of the central ion surroundings. The square of the second moment $\sigma {}^{2} {\left( {\left| {J} \right\rangle } \right)}$ of $\left| {J} \right\rangle $ electronic state CF splitting must be a superposition of squares of the second moments of the partial splittings produced separately by the individual multipoles: $\sigma {}^{2} {\left( {\left| {J} \right\rangle } \right)} = \sum\nolimits_{k} {\sigma _{k}^{2} } {\left( {\left| {J} \right\rangle } \right)} = {\left[ {1/(2J + 1)} \right]}\sum\nolimits_{k} {A_{k}^{2} {\left( {\left| {J} \right\rangle } \right)}} S_{k}^{2} $, where $A_{k} {\left( {\left| {J} \right\rangle } \right)}$ represents the modulus of a k‐rank multipole of the central ion electronic eigenstate $\left| {J} \right\rangle $, whereas $S_{k} = {\left( {[1/(2k + 1)]\sum\nolimits_{q} {\left| {B_{kq} } \right|^{2} } } \right)}^{1/2} $ is the k‐rank CF strength. The relationship between $\sigma {}^{2} {\left( {\left| {J} \right\rangle } \right)}$ known from experiment and $S_{k}^{2} $ obtained from fitting procedure allows us to verify whether the parametrization is physically valid. It is demonstrated by several examples of CF splittings of electronic states of trivalent lanthanide ions in different crystal matrices. The approach is confined only to the states with good quantum numbers J. Nevertheless, by finding such states in any analyzed spectrum, the method can provide the actual multipole characteristics of HCF, and plays the role of a preparametrization. In general, the stepwise fitting procedure can never lead to parametrizations with a correct multipolar structure due to the limitation of the initial eigenfunctions. In consequence, the pertinent crystal‐field parameters (CFPs) are burdened with a methodical inherent fault. The loss of physical meaning of fitted CFPs, its source and consequences, constitute the main theme of the paper.

Multipole fine structure of the cosmic microwave background: reconstruction of the temperature power spectrum

cosmic microwave background (CMB) radiation, CMB temperature autocorrelation, CMB multipole fine structure, temperature fluctuations, temperature anisotropy, spectral fits of CMB multipole moments, spherical Gaussian random field, spherical Green function, covariance matrix, cosmic variance, Hermitian spectral matrix, Gaussian power-law density, Kummer distribution, reconstruction of angular power spectra, inverse problem

MULTIPOLAR PLANETARY NEBULAE: NOT AS GEOMETRICALLY DIVERSIFIED AS THOUGHT

Planetary nebulae (PNe) have diverse morphological shapes, including point-symmetric and multipolar structures. Many PNe also have complicated internal structures such as torus, lobes, knots, and ansae. A complete accounting of all the morphological structures through physical models is difficult. A first step toward such an understanding is to derive the true three-dimensional structure of the nebulae. In this paper, we show that a multipolar nebula with three pairs of lobes can explain many of such features, if orientation and sensitivity effects are taken into account. Using only six parameters - the inclination and position angles of each pair - we are able to simulate the observed images of 20 PNe with complex structures. We suggest that the multipolar structure is an intrinsic structure of PNe and the statistics of multipolar PNe has been severely underestimated in the past.

Precise centering and field characterization of magnetic quadrupole lenses

A setup to investigate fields of magnetic quadrupole lenses was designed and constructed. It allows the spatial position of the axis and the multipole structure of the field of a lens (or lenses) with aperture sizes from 11mm to be determined. The technique employed is based on the measurements of the radial component of the magnetic induction vector using a Hall probe at the points located on the three dimensional surface with subsequent data processing using the Laplace equation. The article presents design and performance characteristics of the setup as well as results from the accuracy evaluations in the measurements of the centers and parasitic multipole field components of the magnetic quadrupole lenses in the integrated doublet.

Spatial and Temporal Evolution of a Multi‐Cell Thunderstorm Charge Structure in Coastal Areas

AbstractThe spatial and temporal variations of charge structure and the relationship with intensity of radar echo of a thunderstorm over low elevation, Shandong of China, have been analyzed with the radiation sources of lightning discharge three‐dimensional mapping system. The results indicate the charge structure was typical dipolar in the convective areas. The intensity of the positive charge region increased and the height of location rose with the development of thunderstorm. The negative charge region was in the area where the intensity of radar echo was more than 40 dBz and the positive charge region was in the 40 dBz radar echo area approximately. The charge structure was also inferred to be dipolar with low charge height and weak charge intensity in stratiform areas. In the dissipation stage of thunderstorm, the charge structure was ruptured for the different dissipation levels of different parts in cloud. The positive and negative charge regions sank in front of the cloud, and the height of the positive and negative charge regions had a little change in the middle part of the cloud, whereas the negative charge region attenuated. So the charge region was four layers in convective areas during dissipation stage. The above results show that the advantage charge generation mechanism often generates dipole or tripole charge structure and does not generate multipole charge structure. This paper also analyzes a negative cloud‐ to‐ground flash discharge process. Its charge structure is the same as the thunderstorm charge structure. So the thunderstorm charge structure can be illustrated by the observations of the three‐dimensional lightning mapping system.

Sound radiation by distributed quadrupole sources near rigid bodies

An approach is proposed to describe the multipole structure of the sound field radiated as a turbulent jet streamlines a transverse circular cylinder of small diameter, which makes it possible to study the experimentally revealed effect of the dipole radiation shift. It is shown that different methods of acoustic measurements can lead to different determinations of the dipole radiation shift. It is demonstrated that to correctly describe the effect of the dipole radiation shift it is necessary to take into account the phase characteristics of different sources in the field of a turbulent flow; i.e., taking into account the state of distribution of the source is of fundamental importance for calculating the dipole radiation shift.

New correlation model for the cascade of turbulent pulsations as a noise source in jets

The mechanisms of noise generation by turbulent jets associated with a cascade of turbulent perturbations are considered from generation of primary eddies to their disintegration. A new correlation model proposed for describing these mechanisms is based on simulation of their generation as a random process with deterministic description of individual eddies. The model makes it possible to analyze available correlation models based on experimental modeling of the correlation function: monopoles, dipoles, or quadrupoles. The main difference between these models is both the different multipole structure of assumed sources and implicit “hard” and “soft” variants of source generation, as well as in the main variable for which the correlation function is developed. This approach is used for developing the correlation model of the noise generation mechanism related to oscillations of surface eddies. The jet noise inferred from the proposed model is well consistent with experimental data on circular jet noise.

An Introduction: Confronting Complexity

In March 2012, a record number of international lawyers assembled in Washington, DC for the 106th Annual Meeting of the American Society of Law. We had the privilege of co-chairing the Meeting and chose as our theme, Confronting Complexity. We felt that this theme reflected well the current challenges and opportunities presented by rapidly evolving technologies, increasing global interconnectedness, rising population, and deepening understanding of science and the environment. New international actors; changes in social, economic, and political dynamics; a multipolar power structure; and novel security threats only add to the complexity we face. Amid this confusion, international law can be a source of order and clarity. It can provide frameworks to resolve disputes peacefully, regulate relations between different actors, and clarify rights and obligations. It can foster technological development and facilitate exchanges of knowledge and goods. It is no surprise that managing global financial crises, protecting global commons, responding to conflicts spilling across borders, and guaranteeing public health and safety have all been added to international law's purview. In our crowded, connected world, civil uprisings, financial collapses, natural and human-caused disasters are no longer domestic crises: they are global crises. While international law has at times been quite creative in response to these problems, whether it is fully up to the task remains an open question. law can actually exacerbate complexity with conflicting or unclear rules, uncertain enforcement, and overlapping and competing jurisdiction. law must demonstrate the flexibility to embrace new issues, to look beyond the state, and to integrate new players (who may not follow its rules). Transparency, accountability, and participation must be guaranteed in new private regulatory regimes, shorn from state control. instruments and processes of international law must provide means for scientific evidence to be sifted, understood, and translated into law. And yet, even as it adapts, international law must also remain a force for stability and predictability. As we looked at various issues that seemed to be defining the moment in international law, whether the Arab Spring, the global financial crisis, disasters, or drone warfare, we kept coming back to this theme of complexity. These issues seemed staggeringly complex, not just for the range of laws and regimes they implicate, but for the masses of information that need to be processed to figure out how to deal with them. More and more, it seemed that the real challenge was understanding how to grasp and manage this increasing complexity. questions we wanted to address at the Annual Meeting were not only how international law might help do this, but also whether international law is always the best tool to do so. We sought to explore when and how international law can best be mobilized and when and how it might either partner with or even cede the field to others. These questions were prominent in the panels, roundtables, and talks scheduled for the Annual Meeting. We sought to tackle the problem of complexity in a number of different ways. First, some sessions featured particularly complex problems, for example, roundtables or panels on International Humanitarian Law and New Technology, Cybersecurity, What Makes a State, International Energy Governance, An Emerging Law of Migration, Financial Crisis in the Eurozone, The Emergence of a Human Right to Water and Sanitation, The Emerging System of Arbitration, Chevron/ Ecuador Dispute: A Paradigm of Complexity, and Transitional Justice and the Arab Spring. Second, other sessions focused on attempts to manage or cut through the complexity, including panels on Indicators in Law, Fact-Finding in Interstate Disputes, Courts, Commissions, and the Complexity of Claims Against States, and Global Environmental Protection and Transnational Conservation Contracts. …

Mergers of black-hole binaries with aligned spins: Waveform characteristics

We conduct a descriptive analysis of the multipolar structure of gravitational-radiation waveforms from equal-mass aligned-spin mergers, following an approach first presented in the complementary context of nonspinning black holes of varying mass ratio [J.G. Baker et al. Phys. Rev. D 78 044046 (2008)]. We find that, as with the nonspinning mergers, the dominant waveform mode phases evolve together in lock-step through inspiral and merger, supporting the previous waveform description in terms of an adiabatically rigid rotator driving gravitational-wave emission-an implicit rotating source. We further apply the late-time merger-ringdown model for the rotational frequency introduced in [J.G. Baker et al. Phys. Rev. D 78 044046 (2008)], along with an improved amplitude model appropriate for the dominant (2, \pm2) modes. This provides a quantitative description of the merger-ringdown waveforms, and suggests that the major features of these waveforms can be described with reference only to the intrinsic parameters associated with the state of the final black hole formed in the merger. We provide an explicit model for the merger-ringdown radiation, and demonstrate that this model agrees to fitting factors better than 95% with the original numerical waveforms for system masses above \sim150M\odot. This model may be directly applicable to gravitational-wave detection of intermediate-mass black-hole mergers.

Fast Multipole Boundary Element Method for 3-Dimension Acoustic Radiation Problem

In order to reduce computational complexity and memory requirements using conventional boundary element method (CBEM) for large scale acoustical analysis, a fast solving algorithm called the Fast Multipole BEM (FMBEM) based on the fast multipole algorithm and GMRES iterative solver is developed without composing the dense influence coefficient matrices. The multipole level structure is introduced to accelerate the solution of large-scale acoustical problems, by employing a concept of cells clustering boundary elements and hierarchical cell structure. To further improve the efficiency of the FMBEM with iterative solvers, a block diagonal matrix method is used in the system of equations as the left pre-conditioner. Numerical examples are presented to further demonstrate the efficiency, accuracy and potentials of the fast multipole BEM for solving large-scale acoustical problems.

A molecular Debye-Hückel theory and its applications to electrolyte solutions

In this report, a molecular Debye-Hückel theory for ionic fluids is developed. Starting from the macroscopic Maxwell equations for bulk systems, the dispersion relation leads to a generalized Debye-Hückel theory which is related to the dressed ion theory in the static case. Due to the multi-pole structure of dielectric function of ionic fluids, the electric potential around a single ion has a multi-Yukawa form. Given the dielectric function, the multi-Yukawa potential can be determined from our molecular Debye-Hückel theory, hence, the electrostatic contributions to thermodynamic properties of ionic fluids can be obtained. Applications to binary as well as multi-component primitive models of electrolyte solutions demonstrated the accuracy of our approach. More importantly, for electrolyte solution models with soft short-ranged interactions, it is shown that the traditional perturbation theory can be extended to ionic fluids successfully just as the perturbation theory has been successfully used for short-ranged systems.