Detecting the superfluid critical momentum of Bose gases in optical lattices through dipole oscillations

We study stability of superflow of Bose gases in optical lattices by analyzing the Bose-Hubbard model within the Gutzwiller mean-field approximation. We calculate the excitation spectra of the homogeneous Bose-Hubbard model at unit filling to determine the critical momenta for the Landau and dynamical instabilities. These two critical momenta are shown to approach each other when the on-site interaction increases towards the Mott transition point. In order to make a direct connection with realistic experiments, we next take into account a parabolic trapping potential and compute the real-time dynamics of dipole oscillations induced by suddenly displacing the trap center. We consider the following two cases: standard softcore bosons, whose interparticle interactions include the on-site one only, and hardcore bosons with long-range dipole-dipole interactions. For both cases, we show that the dipole oscillation is significantly damped when the maximum local momentum exceeds a certain threshold, which quantitatively agrees with the critical momentum for the dynamical instability in the homogeneous system. In the case of dipolar hardcore bosons, the dynamical instability of dipole oscillations leads to the formation of checkerboard density waves in the superfluid phase near the boundary to the supersolid phase.Comment: 21 pages, 27 figure

Ultrastructure of Three Types of Epidermal Dendritic Cells in Hairless Mice*

Electronmicroscopic studies of epidermal dendritic cells in hairless mice were carried out in normal and pigmented dorsal skin, the latter induced by topical application of DMBA. A quantitative study of three types of epidermal dendritic cells was performed in this series. Statistical evaluation disclosed that: (1) the number of Langerhans cells was inversely proportional to that of the melanocytes, and (2) the number of the indeterminate dendritic cells remained constant. A pair of flanking indeterminate dendritic cells which appeared to be divided daughter cells was incidentally found a week after the start of the experiment. Our results suggest that the indeterminate dendritic cell could be an undifferentiated cell which might give rise to either one of the other epidermal dendritic cell types

Molecular Mechanisms of Receptor-Mediated Endocytosis in the Renal Proximal Tubular Epithelium

Receptor-mediated endocytosis is a pivotal function of renal proximal tubule epithelial cells (PTECs) to reabsorb and metabolize substantial amounts of proteins and other substances in glomerular filtrates. The function accounts for the conservation of nutrients, including carrier-bound vitamins and trace elements, filtered by glomeruli. Impairment of the process results in a loss of such substances and development of proteinuria, an important clinical sign of kidney disease and a risk marker for cardiovascular disease. Megalin is a multiligand endocytic receptor expressed at clathrin-coated pits of PTEC, playing a central role in the process. Megalin cooperates with various membrane molecules and interacts with many intracellular adaptor proteins for endocytic trafficking. Megalin is also involved in signaling pathways in the cells. Megalin-mediated endocytic overload leads to damage of PTEC. Further studies are needed to elucidate the mechanism of megalin-mediated endocytosis and develop strategies for preventing the damage of PTEC

Pharyngostomum cordatum in domestic cats in Fukuyama District, Hiroshima Prefecture

1) Pharyngostomum cordatum eggs were detected from 32 domestic cats (1.1%) out of 3,000 examined in Fukuyama District, Hiroshima Prefecture, during the period from 1971 to 1982. 2) Spirometra erinacei was also parasitized at a high rate of 78% in the cats infected with P. cordatum. 3) No relation was found between the infected cats and thier sex, age, or species

The first case of hairworm, Gordius sp. vomited from a domestic dog in Japan

An adult female hairworm was vomited from a domestic dog with a cough in Hiroshima Prefecture. The worm body was long and slender, measuring 42.5 cm in length and 1 mm in maximum width. The specimen showed microscopically the smooth cuticular without tuberculations. This case is the first record of Gordius sp. infection in a dog in Japan