Finite temperature phase diagram of spin-1/2 bosons in two-dimensional optical lattice

We study a two-species bosonic Hubbard model on a two-dimensional square lattice by means of quantum Monte Carlo simulations and focus on finite temperature effects. We show in two different cases, ferro- and antiferromagnetic spin-spin interactions, that the phase diagram is composed of solid Mott phases, liquid phases and superfluid phases. In the antiferromagnetic case, the superfluid (SF) is polarized while the Mott insulator (MI) and normal Bose liquid (NBL) phases are not. On the other hand, in the ferromagnetic case, none of the phases is polarized. The superfluid-liquid transition is of the Berezinsky-Kosterlitz-Thouless type whereas the solid-liquid passage is a crossover.Comment: 9 pages, 13 figure

Ground state phase diagram of spin-1/2 bosons in a two-dimensional optical lattice

We study a two-species bosonic Hubbard model on a two-dimensional square lattice by means of quantum Monte Carlo simulations. In addition to the usual contact repulsive interactions between the particles, the Hamiltonian has an interconversion term which allows the transformation of two particles from one species to the other. The phases are characterized by their solid or superfluid properties and by their polarization, i.e. the difference in the populations. When inter-species interactions are smaller than the intra-species ones, the system is unpolarized, whereas in the opposite case the system is unpolarized in even Mott insulator lobes and polarized in odd Mott lobes and also in the superfluid phase. We show that in the latter case the transition between the Mott insulator of total density two and the superfluid can be either of second or first order depending on the relative values of the interactions, whereas the transitions are continuous in all other cases.Comment: 10 pages, 17 figure

Does raised intraocular pressure begin in utero?

AIM—To determine whether fetal and infant growth, as assessed by weight at birth and weight at 1 year, are related to intraocular pressure.METHODS—717 men and women born in Hertfordshire between 1920 and 1930, for whom records of birth weight and weight at 1 year were available, were examined. Visual fields were assessed using the Takagi central 25 degree 75 point static threshold screening program. Tonometry was performed using the Perkin's tonometer. The disc was assessed by direct ophthalmoscopy through dilated pupils.RESULTS—A significant inverse relation was found between systolic blood pressure and birth weight. However, no association was found between birth weight or weight at 1 year and intraocular pressure, cup/disc ratio, or visual field defects.CONCLUSIONS—There was no evidence to support fetal or infant growth as being important factors for the subsequent development of raised intraocular pressure

Freqüência de sintomas digestivos em pacientes brasileiros com Diabetes Mellitus Digestive symptoms in Brazilian patients with Diabetes Mellitus

Sintomas sugestivos do comprometimento do tubo digestivo são comuns em pacientes diabéticos, mas estudos comparando as freqüências destes sintomas com as da população geral são escassos e não existem trabalhos dessa natureza com diabéticos brasileiros. OBJETIVO: Determinar as freqüências de diferentes sintomas digestivos em amostra não selecionada de pacientes diabéticos, em comparação às encontradas em pessoas da comunidade. MÉTODOS: A ocorrência de 13 diferentes sintomas digestivos foi investigada por meio da aplicação de um questionário padronizado, especificamente estruturado, em 153 diabéticos dos tipos 1 e 2 e em 50 pessoas aparentemente sadias, tomadas como controles. RESULTADOS: A freqüência de diabéticos com pelo menos um sintoma digestivo foi significativamente superior à verificada no grupo controle (70% vs 36%, p = 0,01). Freqüências elevadas de plenitude gástrica (30% vs 36%), pirose (30% vs 34%) e de constipação (17% vs 12%), foram observadas tanto entre os diabéticos como nos controles. No entanto, somente a freqüência de um único sintoma, a disfagia, foi significativamente maior entre os diabéticos, em relação ao grupo controle (13% vs 2%, p = 0,02). CONCLUSÃO: Estes resultados indicam que a freqüência de sintomas digestivos em diabéticos, apesar de elevada, não difere da verificada na população geral, exceto para a disfagia. As freqüências dos diferentes sintomas estiveram próximas das faixas relatadas em estudos do hemisfério Norte, o que não apóia a hipótese de que fatores inerentes ao meio afetam a ocorrência de queixas digestivas em diabéticos.<br>PURPOSE: To determine the frequencies of digestive symptoms in an unselected sample of Brazilian diabetics, in comparison to those verified in the general population. METHODS: The frequencies of 13 digestive symptoms were determined in 153 type 1 and type 2 diabetics and in 50 apparently healthy controls, utilizing a structured, standardized questionnaire. RESULTS: The percentage of diabetics with at least one symptom was significantly higher than in controls (70% vs 36%, p = 0.01). Higher frequencies of upper digestive symptoms, such as postprandial epigastric fullness (30% vs 35%), heartburn (30% vs 34%), as well as constipation (17% vs 12%) were observed in both groups. Nevertheless, only the prevalence of dysphagia (13% vs 2%) was significantly increased (p = 0.02) in diabetics. CONCLUSION: These findings indicate that gastrointestinal symptoms are common in diabetics, but this seems also to be the case in the general population, with the exception of dysphagia. The frequencies of symptoms observed in Brazil were similar to those reported in studies from the North Hemisphere, a finding that does not support the hypothesis that external factors may influence the prevalence of gastrointestinal symptoms in diabetics