5,112 research outputs found

    Critical behavior at edge singularities in one dimensional spin models

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    In ferromagnetic spin models above the critical temperature (T>TcrT > T_{cr}) the partition function zeros accumulate at complex values of the magnetic field (HEH_E) with a universal behavior for the density of zeros \rho (H) \sim | H - H_E |^{\sg}. The critical exponent \sg is believed to be universal at each space dimension and it is related to the magnetic scaling exponent yhy_h via \sg = (d-y_h)/y_h. In two dimensions we have y_h=12/5 (\sg = -1/6) while y_h=2 (\sg=-1/2) in d=1d=1. For the one dimensional Blume-Capel and Blume-Emery-Griffiths models we show here, for different temperatures, that a new value y_h=3 (\sg =-2/3) can emerge if we have a triple degeneracy of the transfer matrix eigenvalues.Comment: to appear in Phys. Rev. E, 16 pages, 3 figure

    From Collected to Collective: strategies for social and political participation through the use of alternative media in Equatorial Guinea

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    Ramón Nsé Esono Ebalé, Josimar Oyono Eseng and Moises Nvumba are responsible for three alternative forms of media concerning Equatorial Guinea: Locos TV [‘Mad TV’], Radio Macuto and the radio station La Voz de los Sin Voz [‘The Voice of the Voiceless’]. None of them are currently living in Equatorial Guinea and they all suffer threats because of exercising their freedom of speech and their criticism of Teodoro Obiang Nguema’s dictatorship.info:eu-repo/semantics/publishedVersio

    Perioperative negative pressure pulmonary edema: case scenario: 2AP2‐11

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    Background: The Negative Pressure Pulmonary Edema (NPPE) is a multifactorial condition,reported in patients af ter general anesthesia. Despite being uncommon (0.05-0.1%),it is a potentially life-threatening emergency that can be fatal in 11-40%.It characteristically occurs af ter endotracheal intubation, but has already been described af ter Laringeal Mask Airway (LMA) use(1). As its occurrence is under-reported, our aim is to point out the importance of an expeditious diagnosis. Case report: 24-yr-old woman (50Kg, 1,60m), presented to the ambulatory surgery center for an a xillary ganglia excisional biopsy. Patient’s medical history was relevant only for a recurrent spontaneous pneumotorax. Unknown allergies.Normal pre-operative study. Inhalatory anesthesia,atraumatic LMA place.Anesthesia and surgical procedure were uneventful. Transferred to Postanesthesia Care Unit (PACU), spontaneously ventilating (SV). Ten minutes later, marked respiratory distress, tachypnea, cyanosis, accessory muscle utilization and significant arterial oxygen desaturation (40%)-treated by positive-pressure mask ventilation until improved peripheral oxygen saturation. Physical examination revealed bilateral dif fuse crackles and respiratory failure type I (PaO2 52mmHg). Chest radiograph with bilateral pulmonary infiltrates without pneumotorax signs. [Image 1] Transferred to Intermediate Care Unit,conscious, hemodynamically stable, SV with supplemental oxygen,SpO2>90%. An echocardiograph(normal) and an angio-computed tomography (acute pulmonary edema in resolution, no signs of thromboembolism) were performed. Progressive recovery without non-invasive pressure support, discharged from hospital on the 4th postoperative day. Follow-up in 8 weeks. Discussion: When considering dif ferential diagnosis of acute-onset perioperative pulmonary edema, NPPE was considered despite the absence of evident high airway obstruction. However, the clinical presentation and its rapid improvement are consistent with the diagnosis. Given the increasing use of LMA, similar episodes can become recurrent, being crucial its prompt recognitio

    Superfluid and Mott Insulating shells of bosons in harmonically confined optical lattices

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    Weakly interacting atomic or molecular bosons in quantum degenerate regime and trapped in harmonically confined optical lattices, exhibit a wedding cake structure consisting of insulating (Mott) shells. It is shown that superfluid regions emerge between Mott shells as a result of fluctuations due to finite hopping. It is found that the order parameter equation in the superfluid regions is not of the Gross-Pitaeviskii type except near the insulator to superfluid boundaries. The excitation spectra in the Mott and superfluid regions are obtained, and it is shown that the superfluid shells posses low energy sound modes with spatially dependent sound velocity described by a local index of refraction directly related to the local superfluid density. Lastly, the Berezinskii-Kosterlitz-Thouless transition and vortex-antivortex pairs are discussed in thin (wide) superfluid shells (rings) limited by three (two) dimensional Mott regions.Comment: 11 pages, 9 figures

    Gravitational wave generation in hybrid quintessential inflationary models

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    We investigate the generation of gravitational waves in the hybrid quintessential inflationary model. The full gravitational-wave energy spectrum is calculated using the method of continuous Bogoliubov coefficients. The post-inflationary kination period, characteristic of quintessential inflationary models, leaves a clear signature on the spectrum, namely, a peak at high frequencies. The maximum of the peak is firmly located at the MHz-GHz region of the spectrum and corresponds to ΩGW1012\Omega_{GW} \simeq 10^{-12}. This peak is substantially smaller than the one appearing in the gravitational-wave energy spectrum of the original quintessential inflationary model, therefore avoiding any conflict with the nucleosynthesis constraint on \Omega_\Omega_{GW}.Comment: 10 pages, 11 figures, one reference adde

    Evolution from BCS to BKT superfluidity in one-dimensional optical lattices

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    We analyze the finite temperature phase diagram of fermion mixtures in one-dimensional optical lattices as a function of interaction strength. At low temperatures, the system evolves from an anisotropic three-dimensional Bardeen-Cooper-Schrieffer (BCS) superfluid to an effectively two-dimensional Berezinskii-Kosterlitz-Thouless (BKT) superfluid as the interaction strength increases. We calculate the critical temperature as a function of interaction strength, and identify the region where the dimensional crossover occurs for a specified optical lattice potential. Finally, we show that the dominant vortex excitations near the critical temperature evolve from multiplane elliptical vortex loops in the three-dimensional regime to planar vortex-antivortex pairs in the two-dimensional regime, and we propose a detection scheme for these excitations.Comment: 4 pages with 2 figure

    Estudio retrospectivo de la eficacia y seguridad del natalizumab en el tratamiento de la esclerosis múltiple en Portugal

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    INTRODUCTION. Studies have shown that natalizumab is an effective treatment for relapsing-remitting multiple sclerosis (RRMS). To date, no data are available in Portuguese patients. AIM. To determine the efficacy and safety of natalizumab in patients with RRMS in routine clinical practice in Portugal. PATIENTS AND METHODS. Clinical data for adult patients with RRMS treated with natalizumab at specialist neurology centres in Portugal were entered retrospectively into a database for analysis between October 2010 and February 2012. Changes in annualized relapse rates (ARR), Expanded Disability Status Scale (EDSS) scores and disability status were analysed. RESULTS. A total of 383 patients from 20 centres were included. Prior to starting natalizumab, the baseline median EDSS score was 4 and the mean ARR was 1.64. Most patients had previously received multiple sclerosis treatment (93.0%). Median natalizumab treatment duration was 12 months. Natalizumab treatment was associated with significant (p = 12 months (n = 288) and for >= 24 months (n = 160). Natalizumab was more effective in patients with less disability (EDSS < 3) and in those who had not previously received disease-modifying treatments. Two cases of progressive multifocal leukoencephalopathy were reported. No new unexpected adverse events occurred. CONCLUSION. Natalizumab is well tolerated, and is effective in reducing relapse rate and stabilising disease in patients with RRMS in the clinical practice setting in Portugal. Its efficacy persists with continued treatment, and it may be particularly effective in patients with less disability and without prior disease modifying therapy.Introduccion. Los estudios han demostrado que el natalizumab constituye un tratamiento eficaz contra la esclerosis multiple remitente recurrente (EMRR). Hasta la fecha, no habia datos de pacientes portugueses. Objetivo. Determinar la eficacia y la seguridad del natalizumab en pacientes con EMRR atendidos en la practica clinica ordinaria en Portugal. Pacientes y metodos. Los datos clinicos de adultos con EMRR tratados con natalizumab en centros especializados de neurologia en Portugal se introdujeron de forma retrospectiva en una base de datos para llevar a cabo un analisis entre octubre de 2010 y febrero de 2012. Se analizo el cambio en la tasa anualizada de brotes (TAB), en las puntuaciones de la escala ampliada de discapacidad (EDSS) y en el estado de discapacidad. Resultados. Se admitio un total de 383 pacientes atendidos en 20 centros. Antes de iniciar el tratamiento con natalizumab, la mediana inicial de la EDSS era de 4,0 y la TAB media, de 1,64. La mayor parte de los pacientes ya habia recibido tratamiento contra la esclerosis multiple (93,0%). La duracion media del tratamiento con natalizumab era de 12 meses. El tratamiento propicio reducciones significativas (p = 12 meses (n = 288) y durante >= 24 meses (n = 160). El natalizumab resulto mas eficaz en los pacientes que presentaban un menor grado de discapacidad (EDSS < 3,0) y en los que no habian recibido ningun tratamiento modificador de la enfermedad. Se notificaron dos casos de leucoencefalopatia multifocal progresiva. No hubo efectos adversos inesperados. Conclusion. El natalizumab presenta una tolerabilidad satisfactoria y se muestra eficaz en la reduccion de las recidivas y la estabilizacion de la EMRR en el marco de la practica clinica ordinaria en Portugal. Conserva su eficacia con el tratamiento continuado y podria ser eficaz especialmente en los pacientes con menos discapacidad y en aquellos que no han recibido ningun tratamiento modificador de la enfermedad hasta el momento

    The politics of autocratic survival in Equatorial Guinea: co-optation, restrictive institutional rules, repression, and international projection

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    Equatorial Guinea is not only one of the world’s most authoritarian regimes but also a striking case of regime and leader survival. This small, oil-rich state and personalist regime defies conventional wisdom because it is both far more resilient and faces far fewer threats from within the regime and from opposition political parties than other resource-rich states. But how does the regime manage to survive? This study argues that four key mechanisms interact to explain Equatorial Guinea’s record of authoritarian survival. Firstly, co-optation (via patronage, party, and cabinet appointments) which President Teodoro Obiang Nguema Mbasogo and the regime party—Partido democrático de guinea ecuatorial—have used to build internal cohesion and fragment opposition. Secondly, the crafting of restrictive institutional rules (party and electoral laws) that, combined with informal rules, aim to protect the regime’s interests and make participation in political opposition more costly. Thirdly, the use of (selective and diffuse) repression to shield the regime and shrink the living space of challengers. Finally, the regime’s international linkages and projection to gain credibility and offset pressure for change. We argue that autocrats’ survival depends on their ability to play a strategic two-level game: domestic and international.info:eu-repo/semantics/acceptedVersio

    Towards Rural Land Use: Challenges for Oversizing Urban Perimeters in Shrinking Towns

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    This article, based on the literature review, aims to study the challenges of the urban dispersion and oversizing of urban perimeters, in the cases where the towns are shrinking or spreading to the rural land-use. It is focused on the case of Portugal where during the last decades there was an escaping to the big cities alongside to the sea (Atlantic and Mediterranean) shore. In the Interior part of the country, which means near to the border with Spain, several towns are shrinking, despite their huge urban perimeters, proposed by the municipal master plans, since the middle of the nineties. Consequently, these urban perimeters are nowadays oversizing, with empty buildings and non-urbanized areas. At the same time, the social patterns of occupation of this territory have changed significantly, moving from a society with signs of rurality to an urban realm, understood not only in territorial terms but also regarding the current lifestyle. This deep changing has occurred not only in urbanistic terms but also in the economic, cultural and social organizations of the country, under a movement that corresponds to a decline of the small urban settlements in rural areas, far away from the cosmopolitan strip of land nearby the sea, in between the capital city, Lisbon and the second one Oporto. These transformations were not driven by any significant public policy for landuse actions. On the contrary, the production of urban areas, supporting the new model of economic and social development was largely left to the initiative of economic and social private agents and land owners. These agents were the leading responsible for the new urban developments and housing. In this sense, this research aims to present some strategies for the short time period regarding the devolution of urban areas to rural land use. In this sense, the next steps of spatial planning policies, under the role of local authorities (the 308 municipalities including Madeira and Azores islands, plus the continental part of the country), which are their main promoters, will be motivated by the need of advocating the swap of many urban areas towards the rural land use, shrinking many existent urban perimeters in depressed territories. How will the non-urbanized spaces, included in the urban perimeters, twenty years ago, by the pivotal instrument of spatial planning in Portugal, the Municipal Master Plans turn back to the rural land-use, losing their market value? This is the base of the challenges ahead, analysed in this article.info:eu-repo/semantics/publishedVersio
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