Retention of differentiated properties in an established dog kidney epithelial cell line (MDCK).

Madin-Darby canine kidney (MDCK) cells grown in tissue culture have the morphological properties of distal tubular epithelial cells, form tight junctions, and lack several proximal tubular enzyme markers. Adenylate cyclase in these cells was stimulated by vasopressin, oxytocin, prostaglandins E1 and E2, glucagon, and cholera toxin. Hormone-stimulated adenylate cyclase activity in isolated membrane preparations was dependent on low concentrations of GTP and had the MgCl2 and pH optima expected for the kidney enzyme. The results, as well as the demonstration of enhanced hemicyst formation induced by cyclic AMP, suggest that the MDCK cell line has retained the differentiated properties of the kidney epithelial cell of origin. When MDCK cells were injected into baby nude mice, continuous nodule growth was observed until adulthood was attained. Histological studies revealed the presence of two cell types: normal mouse fibroblasts which comprise 80--90% of the solid nodule mass, and MDCK cells, which formed epithelial sheets lining internal fluid-filled glands. Electron microscope analysis showed that the mucosal surfaces of the cells were characterized by microvilli which faced the lumen of the glands, that adjacent MDCK cells were joined by tight junctions, and that the serosal surfaces of the epithelial sheets were characterized by smooth plasma membranes which were lined by a continuous basement membrane. These observations lead to the conclusion that the MDCK cells retain regional differentiation of their plasma membranes and the ability to regenerate kidney tubule-like structures in vivo

The Contribution of the Cosmological Constant to the Relativistic Bending of Light Revisited

We study the effect of the cosmological constant $\Lambda$ on the bending of light by a concentrated spherically symmetric mass. Contrarily to previous claims, we show that when the Schwarzschild-de Sitter geometry is taken into account, $\Lambda$ does indeed contribute to the bending.Comment: 5 pages, 2 figure

Gravitomagnetic Resonance Shift due to a Slowly Rotating Compact Star

The effect of a slowly rotating mass on a forced harmonic oscillator with two degrees of freedom is studied in the weak field approximation. It is found that according to the general theory of relativity there is a shift in the resonat frequency of the oscillator which depends on the density and rotational frequency of the gravitational source. The proposed shift is quite small under normal physical situations however it is estimated that for compact x-ray sources such as white dwarfs, pulsars, and neutron stars the shift is quite appreciable.Comment: 8 pages, 2 figures, Accepted for Publication in Inter. Journal of Modern Physics

Rapidly Rotating Bose-Einstein Condensates in Strongly Anharmonic Traps

We study a rotating Bose-Einstein Condensate in a strongly anharmonic trap (flat trap with a finite radius) in the framework of 2D Gross-Pitaevskii theory. We write the coupling constant for the interactions between the gas atoms as $1/\epsilon^2$ and we are interested in the limit $\epsilon\to 0$ (TF limit) with the angular velocity $\Omega$ depending on $\epsilon$. We derive rigorously the leading asymptotics of the ground state energy and the density profile when $\Omega$ tends to infinity as a power of $1/\epsilon$. If $\Omega(\epsilon)=\Omega_0/\epsilon$ a ``hole'' (i.e., a region where the density becomes exponentially small as $1/\epsilon\to\infty$) develops for $\Omega_0$ above a certain critical value. If $\Omega(\epsilon)\gg 1/\epsilon$ the hole essentially exhausts the container and a ``giant vortex'' develops with the density concentrated in a thin layer at the boundary. While we do not analyse the detailed vortex structure we prove that rotational symmetry is broken in the ground state for ${\rm const.}|\log\epsilon|<\Omega(\epsilon)\lesssim \mathrm{const.}/\epsilon$.Comment: LaTex2e, 28 pages, revised version to be published in Journal of Mathematical Physic

Relativistic Hall Effect

We consider the relativistic deformation of quantum waves and mechanical bodies carrying intrinsic angular momentum (AM). When observed in a moving reference frame, the centroid of the object undergoes an AM-dependent transverse shift. This is the relativistic analogue of the spin Hall effect, which occurs in free space without any external fields. Remarkably, the shifts of the geometric and energy centroids differ by a factor of 2, and both centroids are crucial for the correct Lorentz transformations of the AM tensor. We examine manifestations of the relativistic Hall effect in quantum vortices, and mechanical flywheels, and also discuss various fundamental aspects of this phenomenon. The perfect agreement of quantum and relativistic approaches allows applications at strikingly different scales: from elementary spinning particles, through classical light, to rotating black-holes.Comment: 5 pages, 3 figures, to appear in Phys. Rev. Let

Real Time Relativity: exploration learning of special relativity

Real Time Relativity is a computer program that lets students fly at relativistic speeds though a simulated world populated with planets, clocks, and buildings. The counterintuitive and spectacular optical effects of relativity are prominent, while systematic exploration of the simulation allows the user to discover relativistic effects such as length contraction and the relativity of simultaneity. We report on the physics and technology underpinning the simulation, and our experience using it for teaching special relativity to first year university students

Classical tests of general relativity in the Newtonian limit of Schwarzschild-de Sitter spacetime

Recently it has been shown that despite previous claims the cosmological constant affects light bending. In the present article we study light bending and the advance of Mercury's perihelion in the context of the Newtonian limit of Schwarzschild-de Sitter spacetime employing the special relativistic equivalence of mass and energy. In both cases, up to a constant factor, we find the same results as in the full general relativistic treatment of the same phenomena. These approximate and intuitive arguments demonstrate clearly what effects should have been expected from the presence of $\Lambda$ in the general relativistic treatment of these phenomena.Comment: 12 pages, Revtex, 1 figur

Brans-Dicke Gravity from Entropic Viewpoint

We interpret the Brans-Dicke gravity from entropic viewpoint. We first apply the Verlinde's entropic formalism in the Einstein frame, then perform the conformal transformation which connects the Einstein frame to the Jordan frame. The transformed result yields the equation of motion of the Brans-Dicke theory in the Jordan frame.Comment: Title changed, minor changes to match the published versio

Chaotic Accretion in a Non-Stationary Electromagnetic Field of a Slowly Rotating Compact Star

We investigate charge accretion in vicinity of a slowly rotating compact star with a non-stationary electromagnetic field. Exact solutions to the general relativistic Maxwell equations are obtained for a star formed of a highly degenerate plasma with a gravitational field given by the linearized Kerr metric. These solutions are used to formulate and then to study numerically the equations of motion for a charged particle in star's vicinity using the gravitoelectromagnetic force law. The analysis shows that close to the star charge accretion does not always remain ordered. It is found that the magnetic field plays the dominant role in the onset of chaos near the star's surface.Comment: 9 pages, 4 figure