Neutrino masses in lepton number violating mSUGRA

In SUSY models which violate R-parity, there exist trilinear lepton number violating (LNV) operators which can lead to neutrino masses. If these operators are defined at the unification scale, the renormalization group flow becomes important and generally leads to one neutrino mass much heavier than the others. We study, in a minimal supergravity (mSUGRA) set-up with two trilinear LNV operators and three charged lepton mixing angles, numerically how these parameters may be arranged to be compatible with neutrino oscillation data, and discuss some phenomenological observations.Comment: 3 pages, 2 figures. Talk given at SUSY08. To be published in the Conference Proceeding

Casimir probe based upon metallized high Q SiN nanomembrane resonator

We present the instrumentation and measurement scheme of a new Casimir force probe that bridges Casimir force measurements at microscale and macroscale. A metallized high Q silicon nitride nanomembrane resonator is employed as a sensitive force probe. The high tensile stress present in the nanomembrane not only enhances the quality factor but also maintains high flatness over large area serving as the bottom electrode in a sphere-plane configuration. A fiber interferometer is used to readout the oscillation of the nanomembrane and a phase-locked loop scheme is applied to track the change of the resonance frequency. Because of the high quality factor of the nanomembrane and the high stability of the setup, a frequency resolution down to $2\times10^{-9}$ and a corresponding force gradient resolution of 3 $\mu$N/m is achieved. Besides sensitive measurement of Casimir force, our measurement technique simultaneously offers Kelvin probe measurement capability that allows in situ imaging of the surface potentials

Characterization of Metastatic Tumor Formation by the Colony Size Distribution

Knowledge regarding the kinetics of metastatic tumor formation, as related to the growth of the primary tumor, represents a fundamental issue in cancer biology. Using an in vivo mammalian model, we show here that one can obtain useful information from the frequency distribution of the sizes of metastatic colonies in distant organs after serial sectioning and image reconstruction. To explain the experimental findings, we constructed a biophysical model based on the respective growth patterns of the primary tumor and metastases and a stochastic process of metastatic colony formation. Heterogeneous distributions of various biological parameters were considered. We found that the elementary assumption of exponential forms of growth for the primary tumor and metastatic colonies predicts a linear relation on a log-log plot of a metastatic colony size distribution, which was consistent with the experimental results. Furthermore, the slope of the curve signifies the ratio of growth rates of the primary and the metastases. Non-exponential (Gompertzian and logistic) tumor growth patterns were also incorporated into the theory to explain possible deviation from the log-log linear relation. The observed metastasis-free probability also supported the assumption of a time-dependent Poisson process. With this approach, we determined the mechanistic parameters governing the process of metastatogenesis in the lungs for two murine tumor cell lines (KHT and MCaK). Since biological parameters specified in the model could be obtained in the laboratory, a workable metastatic "assay" may be established for various malignancies and in turn contribute in formulating rational treatment regimens for subclinical metastases.Comment: 14 pages, 6 figure

Drivers behind the monitoring effectiveness of global institutional investors: Evidence from earnings management

This paper studies the drivers behind the monitoring effectiveness of institutional investors in curbing earnings management in an international setting. We identify three distinct drivers and propose two competing hypotheses: the hometown advantage hypothesis predicts that because of proximity to monitoring information, domestic institutions have a comparative advantage over foreign institutions in deterring earnings management, whereas the global investor hypothesis predicts that foreign institutions have a comparative advantage because of their proclivity toward activism and ability to deploy superior monitoring technologies. Consistent with the hometown advantage hypothesis, in aggregate, domestic, but not foreign, institutional ownership is associated with less earnings management; the monitoring effectiveness of foreign institutions improves as they gain proximity to monitoring information. Consistent with the global investor hypothesis, the monitoring effectiveness of foreign institutions improves in environments of greater agency conflicts or weaker governance controls or when the gap in monitoring technology between foreign and domestic institutions widens

Grain boundary ferromagnetism in vanadium-doped In2_2O3_3 thin films

Room temperature ferromagnetism was observed in In$_2$O$_3 thin films doped with 5 at.temperatures ranging from 300 to 600$\,^{\circ}{\rm C}$. X-ray absorption fine structure measurement indicated that vanadium was substitutionally dissolved in the In$_2$O$_3$ host lattice, thus excluding the existence of secondary phases of vanadium compounds. Magnetic measurements based on SQUID magnetometry and magnetic circular dichroism confirm that the magnetism is at grain boundaries and also in the grains. The overall magnetization originates from the competing effects between grains and grain boundaries.Comment: 12 pages, 7 figures, 1 table, accepted by Europhysics Letter