The Hubbard model on a complete graph: Exact Analytical results

We derive the analytical expression of the ground state of the Hubbard model with unconstrained hopping at half filling and for arbitrary lattice sites.Comment: Email:[email protected]

Analytical approach to soliton ratchets in asymmetric potentials

We use soliton perturbation theory and collective coordinate ansatz to investigate the mechanism of soliton ratchets in a driven and damped asymmetric double sine-Gordon equation. We show that, at the second order of the perturbation scheme, the soliton internal vibrations can couple {\it effectively}, in presence of damping, to the motion of the center of mass, giving rise to transport. An analytical expression for the mean velocity of the soliton is derived. The results of our analysis confirm the internal mode mechanism of soliton ratchets proposed in [Phys. Rev. E {\bf 65} 025602(R) (2002)].Comment: 9 figures. Submitted to Phys. Rev.

Lymphoscintigraphy with peritumoral injection versus lymphoscintigraphy with subdermal periareolar injection of technetium-labeled human albumin to identify sentinel lymph nodes in breast cancer patients

Background: Preoperative lymphoscintigraphy is without doubt a valid method for the detection of the sentinel lymph node (SLN). There has been considerable debate regarding the optimal site for the introduction of the tracer; various sites include peritumoral (PT), periareolar (PA), subdermal, and intradermal injection Purpose: To evaluate retrospectively the lymphoscintigraphic identification rate of peritumoral (PT) injection versus subdermal periareolar (PA) injection in the detection of SLNs in breast cancer. Material and Methods: Between October 2002 and December 2011, a cohort of 906 consecutive patients with biopsy proven breast cancer underwent 914 SLN biopsy procedures. A total of 339 procedures (Group A) were performed using a peritumoral (PT) deep injection of radiotracer while 575 procedures (Group B) adopted a subdermal periareolar PA injection of radiotracer towards the upper outer quadrant, regardless of the site of the carcinoma. All the patients underwent synchronous excision of the breast cancer and SLN biopsy. Results: SLNs were identified in the lymphoscintigram in 308/339 cases (90.85%) of Group A (PT injection) and in 537/ 575 cases (93.39%) of Group B (PA injection). Furthermore, in 2/339 patients (0.58%) of Group A, internal mammary lymph nodes were found at lymphoscintigraphy, whereas no internal mammary sentinel nodes were found in the Group B patients. The intraoperative identification rate of axillary SLNs was 99.41% (337 of 339) in the Group A patients and 99.65% (573 of 575) in the Group B patients. There was no significant difference in the two groups between the incidence of the number of SLNs detected and the incidence of identification of positive SLNs. Conclusion: PT versus PA injection of radiotracer showed comparable success rates for axillary SLN identification, and can be considered a rapid and reliable method

Soliton ratchets induced by ac forces with harmonic mixing

The ratchet dynamics of a kink (topological soliton) of a dissipative sine-Gordon equation in the presence of ac forces with harmonic mixing (at least bi-harmonic) of zero mean is studied. The dependence of the kink mean velocity on system parameters is investigated numerically and the results are compared with a perturbation analysis based on a point particle representation of the soliton. We find that first order perturbative calculations lead to incomplete descriptions, due to the important role played by the soliton-phonon interaction in establishing the phenomenon. The role played by the temporal symmetry of the system in establishing soliton ratchets is also emphasized. In particular, we show the existence of an asymmetric internal mode on the kink profile which couples to the kink translational mode through the damping in the system. Effective soliton transport is achieved when the internal mode and the external force get phase locked. We find that for kinks driven by bi-harmonic drivers consisting of the superposition of a fundamental driver with its first odd harmonic, the transport arises only due to this {\it internal mode} mechanism, while for bi-harmonic drivers with even harmonic superposition, also a point-particle contribution to the drift velocity is present. The phenomenon is robust enough to survive the presence of thermal noise in the system and can lead to several interesting physical applications.Comment: 9 pages, 13 figure

Compacton existence and spin-orbit density dependence in Bose-Einstein condensates

We demonstrate the existence of compactons matter waves in binary mixtures of Bose-Einstein condensates (BEC) trapped in deep optical lattices (OL) subjected to equal contributions of intra-species Rashba and Dresselhaus spin-orbit coupling (SOC) under periodic time modulations of the intra-species scattering length. We show that these modulations lead to the rescaling of the SOC parameters that involve the density imbalance of the two components. This gives rise to a density-dependent SOC parameters strongly influence the existence and stability of compacton matter waves. The stability of SOC-compactons is investigated both by linear stability analysis and by time integrations of the coupled Gross-Pitaevskii equations. We find that SOC restricts the parameter ranges for stable stationary SOC-compacton existence but, on the other side, it gives a more stringent signature of their occurrence. In particular, SOC-compactons should appear when the intra-species interactions and the number of atoms in the two components are perfectly balanced (or close to being balanced for metastable cases). The possibility to use SOC-compactons as a tool for indirect measurements of the number of atoms and/or the intra-species interactions, is also suggested.Comment: 14 pages, 11 figure

Adiabatic Compression of Soliton Matter Waves

The evolution of atomic solitary waves in Bose-Einstein condensate (BEC) under adiabatic changes of the atomic scattering length is investigated. The variations of amplitude, width, and velocity of soliton are found for both spatial and time adiabatic variations. The possibility to use these variations to compress solitons up to very high local matter densities is shown both in absence and in presence of a parabolic confining potential.Comment: to appear in J.Phys.

Effect of thermal noise on the phase locking of a Josephson fluxon oscillator

The influence of thermal noise on fluxon motion in a long Josephson junction is investigated when the motion is phase locked to an external microwave signal. It is demonstrated that the thermal noise can be treated theoretically within the context of a two-dimensional map that models the dynamics of a single fluxon

Zeranol y metabolitos urinarios de zearalenona en bovinos para carne

El noreste argentino es, por sus características geográficas y ambientales, una región con fuerte potencial para la actividad ganadera. Los rodeos vacunos de esta zona tienen como base alimenticia pastizales y pasturas mejoradas, las que suelen suplementarse con granos, fuentes proteicas y reservas en forma de rollos o silaje. Estos alimentos son sustratos ricos para que especies de hongos produzcan micotoxinas como zearalenona (ZEA). El consumo de ZEA por los animales hace que se excreten diferentes metabolitos en orina entre los que se encuentra el zeranol. Por su parte, la presencia de zeranol en orina es utilizada como indicador del uso indebido de promotores de crecimiento que se hallan prohibidos en el país. El objetivo de este trabajo fue analizar los metabolitos relacionados con la ZEA excretados en la orina de novillos según los siguientes tratamientos: alimentación con un concentrado de ZEA, exposición a la aplicación de zeranol inyectable y acción simultánea de alimentación con un concentrado de ZEA más exposición a la aplicación de zeranol inyectable. Se presentan los perfiles de metabolitos excretados en orina y su evolución en el tiempo.The northern east Argentinean region is, on the basis of its geographic and environmental features, an area with a strong growing cattle potential. Supplementation of natural feeding with protein sources and silage constitutes a usual practice. The feeding supplements supports fungal growth and subsequent micotoxins evolvement as well. Production of zearalenone (ZEA) is particularly relevant because, among its related metabolites excreted in urine there is the zeranol. The zeranol presence in urine is strongly regulated by Argentinean law because it is considered an indicator of forbidden growing promoters using. The objective of the present work was to analyze the ZEA related metabolites excreted in urine of cows exposed to ZEA and/or zeranol in three ways: ZEA concentrated feeding, zeranol injection, and a combined exposure to ZEA concentrate feeding plus zeranol injection. The urine ZEA metabolites profiles and their time evolvement are given.Inst. de PatobiologíaFil: Salvat, Adriana Elisabeth. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patobiología; ArgentinaFil: Comerio, Ricardo Mario. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: Balbuena, Osvaldo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Colonia Benitez; ArgentinaFil: Rosello Brajovich, José Emilio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Colonia Benitez; ArgentinaFil: Ricca, Alejandra Patricia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimentos; ArgentinaFil: Rojas, Dante Emanuel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimentos; ArgentinaFil: Cristos, Diego Sebastian. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimentos; ArgentinaFil: Ronco, S. Servicio Nacional de Sanidad y Calidad Agroalimentaria (SENASA); ArgentinaFil: Salerno, Juan Carlos. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentin

Phonons and solitons in the "thermal" sine-Gordon system

Standard methods of stochastic processes are used to study the coupling of the sine-Gordon system with a heat reservoir. As a result we find thermal phonons with an average energy of kB T per mode. The translational mode (zero mode) is found to carry an average energy of 1/2kBT. This last value is just the energy in the Brownian motion of a thermal soliton. These results are in agreement with those obtained by the use of a statistical-mechanical description of a dilute soliton gas. Connection of the above results with Josephson junctions and the extension of the analysis to more general equations is also discussed