Plasmas confined by a dipole magnetic field exhibit interchange and entropy mode turbulence causing bursty intermittent transport of particles and energy [1]. On the Collisionless Terrella Experiment (CTX), this turbulence is dominated by low-frequency, long-wavelength modes with amplitudes and phases that vary chaotically in time [2]. We present a new paradigm for characterizing this turbulence by measuring the time-evolution of the fluctuation power spectrum and the instantaneous bispectrum using the continuous wavelet transform [3, 4] and computing the statistical properties of turbulent wave kinetics. We observe that both the fluctuation power and the energy transfer by three-wave coupling, or bispectrum, between these fluctuations can be intermittent. When antenna are used to actively launch waves into the turbulence, the intermittency of the driven waves decreases, while the intermittency of other waves increases. Similarly, application of active feedback [5] to amplify the turbulence decreases the intermittency of the wave energy, while suppressing feedback increases this intermittency. Measurements based on this new paradigm show that the transfer of wave energy to larger and smaller scales in a turbulent plasma is not steady but occurs in short and intense bursts, analogous to the better-known short bursts of particle transport in magnetized plasma.

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Com base em trabalhos tanto teóricos como experimentais, tem-se concluído que o Cu+ fica em posição fora de centro em alguns halogenetos alcalinos. Neste, trabalho apresentamos resultados obtidos por técnicas de correntes termoestimuladas(ITC), para, verificar propriedades de dipolos elétricos devido a Íons de Cu+ em posição fora da centro em cristais de KCl. Ampliou-se o estudo do comportamento do Cu+ em cristais de KBr e KI. As bandas de ITC observadas nestes cristais, apresentam máximos em 62, 70 e 83 &#176K, e as energias de ativação são de 0.177, 0.196 e 0.232 eV em KCl, KBr e KI, respectivamente. A partir da integração das bandas de ITC e as concentrações de Cu+ achados por absorção ótica, o momento, dipolar elétrico é determinado, conduzindo a valores de 1.5, 1.9 e 2.6 e &#197 no KCl, KBr e KI, respectivamente. Dada a forma da banda de ITC, comprova-se que a reorientação dos dipo1os segue o modelo clássico com um tempo de relaxação simples, e que o Cu+ fica congelado em posição fora de centro abaixo daquelas temperaturas em que ocorre o máximo da banda de ITC. / Theoretical and experimental investigations have concluded that Cu+ occupies an off-canter position in several alkali halides. In this work we report results obtained by ionic thermal-currents technique (ITC) to verify the electric dipole properties due to Cu+ ions in off-center position in KC1 crystals. This was developed to study the Cu+ ion behaviour in KBr and KI crystals. The ITC band observed in these crystals geve maxima at 62, 70 and 83 &#176K, and the activation energies were 0.177, 0.196 end 0.232 eV in KCI, KBr and KI, respectively. From the integration of the ITC bands and the concentration of Cu+ obtained by optical absorption, the dipole moment is determined, giving values of 1.5, 1.9 and 2.6 e &#197 in KC1, KBr and KI, respectively. Due to the shape of the ITC band, we conclude that the dipole reorientation follows the classical model with a single relaxation time, and that the Cu+ freeze in off-center position below those temperatures where maximum occur at the ITC band.

A Corrente do Brasil é formada na bifurcação do ramo sul da Corrente Sul Equatorial e flui meridionalmente para sul ao largo das costas leste, sudeste e sul do Brasil, apresentando intensa atividade de mesoescala entre a Cadeia Vitória-Trindade (20oS) e o Cabo de Santa Marta Grande (28oS). O conhecimento de tal atividade, construído ao longo do tempo, se refere principalmente aos meandros e vórtices frontais, sendo os vórtices de borda na configuração de dipolos vorticais relatados apenas através de imagens AVHRR. Dessa forma, objetivamos caracterizar a estrutura dinâmica de um dipolo vortical, observado na Bacia de Santos, a partir de dados quase-sinóticos de velocidade e hidrográficos oriundos do Cruzeiro Dinâmica do Ecossistema da Plataforma da Região Oeste do Atlântico Sul V. O mapeamento objetivo das estruturas capturadas pela grade amostral quase-sinótica do cruzeiro foi o ponto de partida para a descrição do dipolo e avaliação de sua geostrofia. Os campos de função de corrente apresentaram um padrão clássico de dipolo vortical, com vórtices ciclônico e anticiclônico posicionados em lados opostos ao eixo da corrente, que se enfraquece após a estrutura. Em média, o diâmetro de ambos os vórtices ficou em torno de 110 km, em seus maiores eixos. Em seguida, como o número de Rossby máximo foi de 0,27, para avançar nas questões dinâmicas envolvendo a estrutura, aproximamos o oceano a um modelo quase-geostrófico de 11/2-camadas derivado das observações e dinamicamente calibrado. A análise dos campos modelados, utilizando o número de Burger, revelou que a vorticidade relativa compete com a vorticidade de estiramento pela dinâmica do sistema. Ao compararmos os campos modelados de função de corrente e vorticidade potencial, observamos que o dipolo e o escoamento da CB não se encontram em um cenário estacionário. Finalmente, evidências de retroalimentação mútua entre os vórtices do dipolo foram obtidas através da interação entre o campo de função de corrente de uma estrutura com o campo de vorticidade potencial da outra. Logo, concluímos que o dipolo capturado encontrava-se em processo de crescimento barotrópico. / The Brazil Current (BC) is formed at the bifurcation of the southern branch of the South Equatorial Current and flows south-southeastward off the east, southeast and southern Brazilian continental margin, exhibiting intense meso-scale activity between the Vitória-Trindade Ridge (20oS) and Cape Santa Marta Grande (28oS). The knowledge of such activity, built over time, refers mainly to the frontal meanders and eddies. The edge vortical structures as a dipole configuration are reported only through AVHRR images. Thus, we aimed to characterize the dynamical structure of a BC vortical dipole, observed in the Santos Basin, with a quasi-synoptic velocity (vessel-mounted ADCP) and hydrographic (CTD) dataset from DEPROAS V cruise. The objective mapping of structures captured by the cruise sampling grid was the departing point for the description of the dipole and evaluation of its degree of geostrophy. The fields of the stream function showed a classic pattern of a dipole with cyclonic and anticyclonic eddies positioned on opposite sides of the current axis. On average, the diameter of the two eddies was around 110 km in their largest axes. Then, as the Rossby number was 0.27, we advanced in investigating the issues involving the dynamic structure by we approximating the ocean to a 11/2 layer quasi-geostrofic model derived from the observations and dynamically calibrated. Burger number revealed that both relative and stretching vorticity were competing for the dynamics of the system. The comparison between the modeled stream function and potential vorticity fields showed that both the dipole and the BC flow were not in a stationary state. Finally, evidences of reinforcement between the eddies of the dipole were obtained through the interaction between the field of the stream function of vortical structure with the field of potential vorticity of the other one, and vice-versa. Therefore, we conclude that the dipole were in a barotropic growth process.

[by] J.M. Luttinger and L. Tisza. / "Reprinted from the Physical review, vol. 70, nos. 11 and 12, 954-964, Dec. 1 and 15, 1946." / Includes bibliographical references. / Contract OEMsr-262.

The character theory of the symmetric group is a powerful method of studying enu- merative questions about factorizations of permutations, which arise in areas including topology, geometry, and mathematical physics. This method relies on having an encoding of the enumerative problem in the centre Z(n) of the algebra C[S_n] spanned by the symmetric group S_n. This thesis develops methods to deal with permutation factorization problems which cannot be encoded in Z(n). The (p,q,n)-dipole problem, which arises in the study of connections between string theory and Yang-Mills theory, is the chief problem motivating this research. This thesis introduces a refinement of the (p,q,n)-dipole problem, namely, the (a,b,c,d)- dipole problem. A Join-Cut analysis of the (a,b,c,d)-dipole problem leads to two partial differential equations which determine the generating series for the problem. The first equation determines the series for (a,b,0,0)-dipoles, which is the initial condition for the second equation, which gives the series for (a,b,c,d)-dipoles. An analysis of these equa- tions leads to a process, recursive in genus, for solving the (a,b,c,d)-dipole problem for a surface of genus g. These solutions are expressed in terms of a natural family of functions which are well-understood as sums indexed by compositions of a binary string. The combinatorial analysis of the (a,b,0,0)-dipole problem reveals an unexpected fact about a special case of the (p,q,n)-dipole problem. When q=n−1, the problem may be encoded in the centralizer Z_1(n) of C[S_n] with respect to the subgroup S_{n−1}. The algebra Z_1(n) has many combinatorially important similarities to Z(n) which may be used to find an explicit expression for the genus polynomials for the (p,n−1,n)-dipole problem for all values of p and n, giving a solution to this case for all orientable surfaces. Moreover, the algebraic techniques developed to solve this problem provide an alge- braic approach to solving a class of non-central problems which includes problems such as the non-transitive star factorization problem and the problem of enumerating Z_1- decompositions of a full cycle, and raise intriguing questions about the combinatorial significance of centralizers with respect to subgroups other than S_{n−1}.

<p>For some cases of lattice layout in particle accelerators, the major part of the energy deposition coming from the collision is located in the midplane of the magnets. The heat produced might result in a quench in superconducting magnets. One solution for reducing the energy deposition in the coil is to introduce an opening in the midplane, which will lead away most of the particles to a safe zone instead of hitting the superconductors in the magnets.</p><p>The aim of this work is to optimize the field quality in dipoles based on the cosθ-design, where an opening in the midplane has been inserted. The equations for finding the solutions for the coil layout for different sizes of the opening are studied, and the solution giving the best field quality for each case is presented. Then, optimization procedures are applied to lay-outs with Rutherford cables. Finally, the resulting field strength from the solutions obtained is presented.</p>

The Fermilab Tevatron is currently the world’s highest energy colliding beam facility. Its counter-rotating proton and antiproton beams collide at 2 TeV center-of-mass. Delivery of such intense beam fluxes to experiments has required improved knowledge of the Tevatron’s beam optical lattice. An oscillating dipole magnet, referred to as an AC dipole, is one of such a tool to non-destructively assess the optical properties of the synchrotron. We discusses development of an AC dipole system for the Tevatron, a fast-oscillating (f∼20 kHz) dipole magnet which can be adiabatically turned on and off to establish sustained coherent oscillations of the beam particles without affecting the transverse emittance. By utilizing an existing magnet and a higher power audio amplifier, the cost of the Tevatron AC dipole system became relatively inexpensive. We discuss corrections which must be applied to the driven oscillation measurements to obtain the proper interpretation of beam optical parameters from AC dipole studies. After successful operations of the Tevatron AC dipole system, AC dipole systems, similar to that in the Tevatron, will be build for the CERN LHC. We present several measurements of linear optical parameters (beta function and phase advance) for the Tevatron, as well as studies of non-linear perturbations from sextupole and octupole elements. / text

Although current classical force fields describe homogeneous single-componentsystems fairly well, they do not represent the response of an individual molecule's electronic structure to its local environment with enough detail to reliably predict atomic motions in interfacial regions such as a solvation structure or liquid surface.Since most chemical processes of non-trivial interest involve two or more dissimilar molecules interacting at a short distance, molecular models must accurately simulate the interactions between different molecular species as well as bulk behavior in order to provide useful information. Results from two simulation studies are presented to illustrate both the utility of current point-charge electrostatics models in liquid structure determination and the critical importance of modeling induction effects in liquid water.

For some cases of lattice layout in particle accelerators, the major part of the energy deposition coming from the collision is located in the midplane of the magnets. The heat produced might result in a quench in superconducting magnets. One solution for reducing the energy deposition in the coil is to introduce an opening in the midplane, which will lead away most of the particles to a safe zone instead of hitting the superconductors in the magnets. The aim of this work is to optimize the field quality in dipoles based on the cosθ-design, where an opening in the midplane has been inserted. The equations for finding the solutions for the coil layout for different sizes of the opening are studied, and the solution giving the best field quality for each case is presented. Then, optimization procedures are applied to lay-outs with Rutherford cables. Finally, the resulting field strength from the solutions obtained is presented.