2,875 research outputs found
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 and a
corresponding force gradient resolution of 3 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
Na/H Exchange Inhibition Protects Newborn Heart From Ischemia/Reperfusion Injury by Limiting Na+-dependent Ca2+ Overload
The results of the Guardian/Expedition trials demonstrate the need for more precisely controlled studies to inhibit Na/H exchange (NHE1) during ischemia/reperfusion. This is because overwhelming evidence is consistent with the hypothesis that myocardial ischemic injury results in part from increases in intracellular Na (Nai) mediated by NHE1 that in turn promote Na/Ca exchanger-mediated increases in intracellular Ca ([Ca]i) and Ca-dependent cell damage. We used a more potent and specific NHE1 inhibitor HOE 694 (HOE) to test whether inhibition of NHE1 during ischemia limits increases in Nai and [Ca]i in newborns. NMR was used to measure pHi, Nai, [Ca]i, and ATP in isolated newborn rabbit hearts. Perfusion pressure, left ventricular developed pressure, and creatine kinase were measured. HOE was added before global ischemia. Results are reported as mean +/- SE. Nai (mEq/kg dry weight) rose from 11.6 +/- 0.9 before ischemia to 114.0 +/- 16.1 at the end of ischemia and recovered to 55.2 +/- 11.8 in the control group. During ischemia and reperfusion, the corresponding values for Nai in the HOE group (63.1 +/- 8.4 and 15.9 +/- 2.5, respectively, P < 0.05) were lower than control. In the control group [Ca]i (nM/L) rose from 331 +/- 41 to 1069 +/- 71 and recovered to 814 +/- 51, whereas in the HOE group [Ca]i rose less (P < 0.05): 359 +/- 50, 607 +/- 85, and 413 +/- 40, respectively. Total creatine kinase release was significantly reduced in the HOE group. Perfusion pressure and left ventricular developed pressure also recovered significantly better in the HOE group than in the control. In conclusion, NHE1 inhibition diminishes ischemia-induced increases in Nai and therefore [Ca], and thus diminishes myocardial injury in neonatal hearts
Grain boundary ferromagnetism in vanadium-doped InO thin films
Room temperature ferromagnetism was observed in InO\,^{\circ}{\rm C}_2_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
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