20,203 research outputs found
Searching for physics beyond the Standard Model through the dipole interaction
The magnetic dipole interaction played a central role in the development of
QED, and continued in that role for the Standard Model. The muon anomalous
magnetic moment has served as a benchmark for models of new physics, and the
present experimental value is larger than the standard-model value by more than
three standard deviations. The electric dipole moment (EDM) violates parity
({}) and time-reversal ({}) symmetries, and in the context of the
theorem, the combination of charge conjugation and parity (). Since a new
source of {} violation outside of that observed in the and meson
systems is needed to help explain the baryon asymmetry of the universe,
searches for EDMs are being carried out worldwide on a number of systems. The
standard-model value of the EDM is immeasurably small, so any evidence for an
EDM would signify the observation of new physics. Unique opportunities exist
for EDM searches using polarized proton, deuteron or muon beams in storage
rings. This talk will provide an overview of the theory of dipole moments, and
the relevant experiments. The connection to the transition dipole moment that
could produce lepton flavor violating interactions such as is also mentioned.Comment: Invited Plenary talk at the 19th International Spin Physics
Symposium, Juelic
Nucleoside-Diphosphate-Kinase of P. gingivalis is Secreted from Epithelial Cells In the Absence of a Leader Sequence Through a Pannexin-1 Interactome
Nucleoside-diphosphate-kinases (NDKs) are leaderless, multifunctional enzymes. The mode(s) of NDK secretion is currently undefined, while extracellular translocation of bacterial NDKs is critical for avoidance of host pathogen clearance by opportunistic pathogens such as Porphyromonas gingivalis. P. gingivalis-NDK during infection inhibits extracellular-ATP (eATP)/P2X7-receptor mediated cell death in gingival epithelial cells (GECs) via eATP hydrolysis. Furthermore, depletion of pannexin-1-hemichannel (PNX1) coupled with P2X7-receptor blocks the infection-induced eATP release in GECs, and P. gingivalis-NDK impacts this pathway. Ultrastructural and confocal microscopy of P. gingivalis-co-cultured GECs or green-fluorescent-protein (GFP)-P. gingivalis-NDK transfected GECs revealed a perinuclear/cytoplasmic localization of NDK. eATP stimulation induced NDK recruitment to the cell periphery. Depletion of PNX1 by siRNA or inhibition by probenecid resulted in significant blocking of extracellular NDK activity and secretion using ATPase and ELISA assays. Co-immunoprecipitation-coupled Mass-spectrometry method revealed association of P. gingivalis-NDK to the myosin-9 motor molecule. Interestingly, inhibition of myosin-9, actin, and lipid-rafts, shown to be involved in PNX1-hemichannel function, resulted in marked intracellular accumulation of NDK and decreased NDK secretion from infected GECs. These results elucidate for the first time PNX1-hemichannels as potentially main extracellular translocation pathway for NDKs from an intracellular pathogen, suggesting that PNX1-hemichannels may represent a therapeutic target for chronic opportunistic infections
Status of the Fermilab Muon (g-2) Experiment
The New Muon Collaboration at Fermilab has proposed to measure the
anomalous magnetic moment of the muon, , a factor of four better than
was done in E821 at the Brookhaven AGS, which obtained ppm. The last digit of is changed
from the published value owing to a new value of the ratio of the
muon-to-proton magnetic moment that has become available. At present there
appears to be a difference between the Standard-Model value and the measured
value, at the standard deviation level when electron-positron
annihilation data are used to determine the lowest-order hadronic piece of the
Standard Model contribution. The improved experiment, along with further
advances in the determination of the hadronic contribution, should clarify this
difference. Because of its ability to constrain the interpretation of
discoveries made at the LHC, the improved measurement will be of significant
value, whatever discoveries may come from the LHC.Comment: Proceedings of the PhiPsi09, Oct. 13-16, 2009, Beijing, China, 4
pages 2 figures. Version 2 includes Fermilab report number, minor corrections
and one additional referenc
Impacts of Highway Infrastructure Investment Under the American Recovery and Reinvestment Act
This study evaluated the impact on highway demand of highway disbursements under the American Recovery and Reinvestment Act (ARRA). Vehicle miles traveled were used to estimate a highway demand equation employing a spatial Durbin model for the 48 contiguous U.S. states during 1994-2008. Estimates from the equation were used to test the hypothesis that highway disbursements caused different upward shifts in the highway demand curves of states. We estimated 27.2 billion in ARRA highway disbursements, yielding an average net benefit of $0.30 per dollar spent
Off Mass Shell Effects in Hadron Electric Dipole Moments
We note that off the quark mass shell the operators
and , both of which reduce to
in the non-relativistic limit, are no longer
identical. In this paper we explore the effects of this difference in the
contribution of these quark electric moments to hadronic electric moments.Comment: 21 pages, 1 figure, Revtex, uses psfi
Indoor multipath effect study on the Locata system
GNSS has become one of the most wide- spread measurement technologies, allowing cm-level positioning accuracy using RTK or Network RTK. Unfortunately, the system’s major drawbacks are the requirement for a clear view of the sky and accu- racy dependent on the geometric distribution of the satellites, not only varying throughout the day but also prone to location specific problems. With wide- spread utilisation of GNSS for monitoring of man- made structures and other civil engineering tasks, such shortcomings can be critical.
One of possible solution is the deployment of a sup- porting system, such as Locata – a terrestrial posi- tioning technology, which mitigates the need for a clear view of the sky and provides system integrity control.
This paper, part of the proposed integration feasibil- ity study, presents Locata performance indoors, its capacity and mitigation methods
Gas-grain models for interstellar anion chemistry
Long-chain hydrocarbon anions CnH- (n=4, 6, 8) have recently been found to be
abundant in a variety of interstellar clouds. In order to explain their large
abundances in the denser (prestellar/protostellar) environments, new chemical
models are constructed that include gas-grain interactions. Models including
accretion of gas-phase species onto dust grains and cosmic-ray-induced
desorption of atoms are able to reproduce the observed anion-to-neutral ratios,
as well as the absolute abundances of anionic and neutral carbon chains, with a
reasonable degree of accuracy. Due to their destructive effects, the depletion
of oxygen atoms onto dust results in substantially greater polyyne and anion
abundances in high-density gas (with n_{H_2} >~ 10^5 cm^{-3}). The large
abundances of carbon-chain-bearing species observed in the envelopes of
protostars such as L1527 can thus be explained without the need for warm
carbon-chain chemistry. The C6H- anion-to-neutral ratio is found to be most
sensitive to the atomic O and H abundances and the electron density. Therefore,
as a core evolves, falling atomic abundances and rising electron densities are
found to result in increasing anion-to-neutral ratios. Inclusion of cosmic-ray
desorption of atoms in high-density models delays freeze-out, which results in
a more temporally-stable anion-to-neutral ratio, in better agreement with
observations. Our models include reactions between oxygen atoms and
carbon-chain anions to produce carbon-chain-oxide species C6O, C7O, HC6O and
HC7O, the abundances of which depend on the assumed branching ratios for
associative electron detachment
The chemical composition of planetary nebulae and HII regions in NGC 3109
We present deep spectrophotometry for a sample of 8 PNe and 12 HII regions in
the irregular galaxy NGC 3109, to analyze the chemical composition of both
types of nebulae. We present line intensities and the physical conditions and
the abundances of He, O, Ne, N, S and Ar are derived, using the classical
T_e-based method. We confirm our previous identification of PNe and HII regions
based on photometry, except for one object that we argue is a compact HII
region rather than a PN. We find that the chemical composition of the ISM in
NGC 3109, as sampled by its HII regions, is remarkably uniform. The oxygen
abundance is log O/H + 12 = 7.77 \pm 0.07 in this galaxy, as compared to 8.05
\pm 0.09 for the SMC. PNe show significantly higher oxygen abundances in NGC
3109: log O/H + 12 = 8.16 \pm 0.19. We argue that, similarly to what has been
suggested for some of the PNe in the Magellanic Clouds and other metal-poor
galaxies, oxygen in the PNe in NGC 3109 is affected by dredge up in their
progenitors. This could be also the case for neon. From our analysis, we
conclude that these two elements are not always a safe indicator of the
chemical composition of the ISM at low metallicities. An alternative to the O
and Ne enrichment in PNe is that the low metallicity in HII regions has been
caused by dilution of the ISM due interaction with a neighbor galaxy about a
Gyr ago.
The excitation patterns of the PNe in NGC 3109 are very different from the
excitation patterns of PNe in other galaxies. This would imply that the
evolution of PNe depends upon the properties of their progenitor stellar
populations, which vary from galaxy to galaxy. This should affect the PN
luminosity function and its use as a distance indicator.Comment: 14 pages, 9 figures. Accepted in A&A. Final versio
- …