Quantum Phase Transition in Lattice Model of Unconventional Superconductors

In this paper we shall introduce a lattice model of unconventional superconductors (SC) like d-wave SC in order to study quantum phase transition at vanishing temperature ($T$). Finite-$T$ counterpart of the present model was proposed previously with which SC phase transition at finite $T$ was investigated. The present model is a noncompact U(1) lattice-gauge-Higgs model in which the Higgs boson, the Cooper-pair field, is put on lattice links in order to describe d-wave SC. We first derive the model from a microscopic Hamiltonian in the path-integral formalism and then study its phase structure by means of the Monte Carlo simulations. We calculate the specific heat, monopole densities and the magnetic penetration depth (the gauge-boson mass). We verified that the model exhibits a second-order phase transition from normal to SC phases. Behavior of the magnetic penetration depth is compared with that obtained in the previous analytical calculation using XY model in four dimensions. Besides the normal to SC phase transition, we also found that another second-order phase transition takes place within the SC phase in the present model. We discuss physical meaning of that phase transition.Comment: 12 pages, 10 figures, references added, some discussion on the results adde

Measurement of allergen-specific secretory IgA in stool of neonates, infants and toddlers by protection against degradation of immunoglobulins and allergens

Background and aims : Measurement of secretory immunoglobulin A (SIgA) level is important to monitor various disease conditions. However SIgA in gut mucosa is degraded by pancreatic proteases and proteolytic enzymes from enteric microbiota. Currently, there is no reliable quantitation method that measures allergen-specific SIgA levels in stool of neonates, infants and toddlers. Methods : Allergen-specific SIgA levels in stool of 10 healthy neonates, infants and toddlers aged 0 to 36 months were measured by our new allergen microarray with densely carboxylated arms on a glass slide chip. Results : Protease activities in stool of 3-day-old neonates were low and no degradation of SIgA, IgA and allergens was detected. However, immunofluorescence signals of SIgA, IgA and allergen on the chip were markedly reduced by stool extracts obtained from infants and toddlers aged more than one month in dose- and time-dependent manners. Such reduction was almost completely inhibited by serine protease inhibitors, phenylmethylsulfonyl fluoride (PMSF) and partly by leupeptin, but not by a variety of other protease inhibitors tested. Conclusion : Allergen-specific SIgA levels in stool of neonates, infants and toddlers under 36 months of age could be analyzed using protease inhibitors, including PMSF and leupeptin

Development of catheter-type tactile sensor composed of polyvinylidene fluoride (PVDF) film

To achieve quantitative palpation in vivo, we developed a catheter-type tactile sensor composed of a polyvinylidene fluoride film for minimally invasive surgery. We evaluated the fundamental performance of the prototype sensor by a weight-drop test. We also measured the output of the prototype sensor as it was inserted into a blood vessel model with shapes mimicking lesions. The ø2-mm sensor passed easily into the blood vessel model with lesion-like shapes. Sensor outputs corresponded to the shape of the inner wall of the blood vessel model, making it possible to determine the position of a protrusion and the convexity interval of a rough surface by filtering and frequency analysis of the output