4,289 research outputs found
Signals of Unparticles in Low Energy Parity Violation and NuTeV Experiment
We have studied the possible signals of unparticle in atomic parity
violation(APV) along an isotope chain and in the NuTeV experiment. The effects
of unparticle physics could be observed in APV, if the uncertainty in relative
neutron/proton radius shift is less than a few
times by measuring the parity violating electron scattering. The
constraints imposed by NuTeV experiment on unparticle physics are discussed in
detail. If the NuTeV results are confirmed by future experiments, we suggest
that unparticle could account for a part of NuTeV anomaly. There exist certain
regions for the unparticle parameters (, ,
and ), where the NuTeV discrepancy could be
completely explained by unparticle effects and the strange quark asymmetry,
even with or without the contributions from the isoscalarity violation etc. It
is remarkable that these parameter regions are consistent with the constraints
from Comment: 19 pages, 7 figure
Online Updating of Statistical Inference in the Big Data Setting
We present statistical methods for big data arising from online analytical
processing, where large amounts of data arrive in streams and require fast
analysis without storage/access to the historical data. In particular, we
develop iterative estimating algorithms and statistical inferences for linear
models and estimating equations that update as new data arrive. These
algorithms are computationally efficient, minimally storage-intensive, and
allow for possible rank deficiencies in the subset design matrices due to
rare-event covariates. Within the linear model setting, the proposed
online-updating framework leads to predictive residual tests that can be used
to assess the goodness-of-fit of the hypothesized model. We also propose a new
online-updating estimator under the estimating equation setting. Theoretical
properties of the goodness-of-fit tests and proposed estimators are examined in
detail. In simulation studies and real data applications, our estimator
compares favorably with competing approaches under the estimating equation
setting.Comment: Submitted to Technometric
Rapid collapse of spin waves in non-uniform phases of the second Landau level
The spin degree of freedom in quantum phases of the second Landau level is
probed by resonant light scattering. The long wavelength spin wave, which
monitors the degree of spin polarization, is at the Zeeman energy in the fully
spin-polarized state at =3. At lower filling factors the intensity of the
Zeeman mode collapses indicating loss of polarization. A novel continuum of
low-lying excitations emerges that dominates near =8/3 and =5/2.
Resonant Rayleigh scattering reveals that quantum fluids for break up
into robust domain structures. While the state at =5/2 is considered to be
fully polarized, these results reveal unprecedented roles for spin degrees of
freedom.Comment: 4 pages, 5 figure
Experimental high-intensity three-photon entangled source
We experimentally realize a high-intensity three-photon
Greenberger-Horne-Zeilinger (GHZ) entanglement source directly following the
proposal by Rarity and Tapster [J. G. Rarity and P. R. Tapster, Phys. Rev. A
59, R35 (1999)]. The threefold coincidence rate can be more than 200 Hz with a
fidelity of 0.811, and the intensity can be further improved with moderate
fidelity degradation. The GHZ entanglement is characterized by testing the
Bell-Mermin inequality and using an entanglement witness operator. To optimize
the polarization-entangled source, we theoretically analyze the relationship
between the mean photon number of the single-photon source and the probability
of parametric down-conversion.Comment: 4 pages, 4 figure
Reduced dynamics with renormalization in solid-state charge qubit measurement
Quantum measurement will inevitably cause backaction on the measured system,
resulting in the well known dephasing and relaxation. In this report, in the
context of solid--state qubit measurement by a mesoscopic detector, we show
that an alternative backaction known as renormalization is important under some
circumstances. This effect is largely overlooked in the theory of quantum
measurement.Comment: 12 pages, 4 figure
Distinct features of nucleolus-associated domains in mouse embryonic stem cells [preprint]
Background Heterochromatin in eukaryotic interphase cells frequently localizes to the nucleolar periphery (nucleolus-associated domains, NADs) and the nuclear lamina (lamina-associated domains, LADs). Gene expression in somatic cell NADs is generally low, but NADs have not been characterized in mammalian stem cells. Results Here, we generated the first genome-wide map of NADs in mouse embryonic stem cells (mESCs) via deep sequencing of chromatin associated with biochemically-purified nucleoli. As we had observed in mouse embryonic fibroblasts (MEFs), the large Type I subset of NADs overlaps with constitutive LADs and is enriched for features of constitutive heterochromatin, including late replication timing and low gene density and expression levels. Conversely, the Type II NAD subset overlaps with loci that are not lamina-associated, but in mESCs, Type II NADs are much less abundant than in MEFs. mESC NADs are also much less enriched in H3K27me3 modified regions than are NADs in MEFs. Additionally, comparision of MEF and mESC NADs revealed enrichment of developmentally regulated genes in cell type-specific NADs. Together, these data indicate that NADs are a developmentally dynamic component of heterochromatin. Conclusions These studies implicate association with the nucleolar periphery as a mechanism for developmentally-regulated gene silencing, and will facilitate future studies of NADs during mESC differentiation
Genome-Wide Expression Analysis Reveals Diverse Effects of Acute Nicotine Exposure on Neuronal Function-Related Genes and Pathways
Previous human and animal studies demonstrate that acute nicotine exposure has complicated influences on the function of the nervous system, which may lead to long-lasting effects on the behavior and physiology of the subject. To determine the genes and pathways that might account for long-term changes after acute nicotine exposure, a pathway-focused oligoarray specifically designed for drug addiction research was used to assess acute nicotine effect on gene expression in the neuron-like SH-SY5Y cells. Our results showed that 295 genes involved in various biological functions were differentially regulated by 1 h of nicotine treatment. Among these genes, the expression changes of 221 were blocked by mecamylamine, indicating that the majority of nicotine-modulated genes were altered through the nicotinic acetylcholine receptors (nAChRs)-mediated signaling process. We further identified 14 biochemical pathways enriched among the nicotine-modulated genes, among which were those involved in neural development/synaptic plasticity, neuronal survival/death, immune response, or cellular metabolism. In the genes significantly regulated by nicotine but blocked by mecamylamine, 13 enriched pathways were detected. Nine of these pathways were shared with those enriched in the genes regulated by nicotine, including neuronal function-related pathways such as glucocorticoid receptor signaling, p38 MAPK signaling, PI3K/AKT signaling, and PTEN signaling, implying that nAChRs play important roles in the regulation of these biological processes. Together, our results not only provide insights into the mechanism underlying the acute response of neuronal cells to nicotine but also provide clues to how acute nicotine exposure exerts long-term effects on the nervous system
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