1,655 research outputs found
Microwave traps for cold polar molecules
We discuss the possibility of trapping polar molecules in the standing-wave
electromagnetic field of a microwave resonant cavity. Such a trap has several
novel features that make it very attractive for the development of ultracold
molecule sources. Using commonly available technologies, microwave traps can be
built with large depth (up to several Kelvin) and acceptance volume (up to
several cm^3), suitable for efficient loading with currently available sources
of cold polar molecules. Unlike most previous traps for molecules, this
technology can be used to confine the strong-field seeking absolute ground
state of the molecule, in a free-space maximum of the microwave electric field.
Such ground state molecules should be immune to inelastic collisional losses.
We calculate elastic collision cross-sections for the trapped molecules, due to
the electrical polarization of the molecules at the trap center, and find that
they are extraordinarily large. Thus, molecules in a microwave trap should be
very amenable to sympathetic and/or evaporative cooling. The combination of
these properties seems to open a clear path to producing large samples of polar
molecules at temperatures much lower than has been possible previously.Comment: 10 pages, 3 figure
A role for the cleaved cytoplasmic domain of E-cadherin in the nucleus
Cell-cell contacts play a vital role in intracellular signaling, although the molecular mechanisms of these signaling pathways are not fully understood. E-cadherin, an important mediator of cell-cell adhesions, has been shown to be cleaved by γ-secretase. This cleavage releases a fragment of E-cadherin, E-cadherin C-terminal fragment 2 (E-cad/CTF2), into the cytosol. Here, we study the fate and function of this fragment. First, we show that coexpression of the cadherin-binding protein, p120 catenin (p120), enhances the nuclear translocation of E-cad/CTF2. By knocking down p120 with short interfering RNA, we also demonstrate that p120 is necessary for the nuclear localization of E-cad/CTF2. Furthermore, p120 enhances and is required for the specific binding of E-cad/CTF2 to DNA. Finally, we show that E-cad/CTF2 can regulate the p120-Kaiso-mediated signaling pathway in the nucleus. These data indicate a novel role for cleaved E-cadherin in the nucleus
An ion ring in a linear multipole trap for optical frequency metrology
A ring crystal of ions trapped in a linear multipole trap is studied as a
basis for an optical frequency standard. The equilibrium conditions and cooling
possibilities are discussed through an analytical model and molecular dynamics
simulations. A configuration which reduces the frequency sensitivity to the
fluctuations of the number of trapped ions is proposed. The systematic shifts
for the electric quadrupole transition of calcium ions are evaluated for this
ring configuration. This study shows that a ring of 10 or 20 ions allows to
reach a short term stability better than for a single ion without introducing
limiting long term fluctuations
Electric-field-induced lifting of the valley degeneracy in alpha-(BEDT-TTF)_2I_3 Dirac-like Landau levels
The relativistic Landau levels in the layered organic material
alpha-(BEDT-TTF)_2I_3 [BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene] are
sensitive to the tilt of the Dirac cones, which, as in the case of graphene,
determine the low-energy electronic properties under appropriate pressure. We
show that an applied inplane electric field, which happens to be in competition
with the tilt of the cones, lifts the twofold valley degeneracy due to a
different level spacing. The scenario may be tested in infrared transmission
spectroscopy.Comment: 4 pages, 1 figure; version with minor corrections published in EP
Calculation of atmospheric neutrino flux using the interaction model calibrated with atmospheric muon data
Using the ``modified DPMJET-III'' model explained in the previous paper, we
calculate the atmospheric neutrino flux. The calculation scheme is almost the
same as HKKM04 \cite{HKKM2004}, but the usage of the ``virtual detector'' is
improved to reduce the error due to it. Then we study the uncertainty of the
calculated atmospheric neutrino flux summarizing the uncertainties of
individual components of the simulation. The uncertainty of -production in
the interaction model is estimated by modifying FLUKA'97 and Fritiof 7.02 so
that they also reproduce the atmospheric muon flux data correctly, and the
calculation of the atmospheric neutrino flux with those modified interaction
models. The uncertainties of the flux ratio and zenith angle dependence of the
atmospheric neutrino flux are also studied
Feasibility of a storage ring for polar molecules in strong-field-seeking states
We show, through modeling and simulation, that it is feasible to construct a
storage ring that will store dense bunches of strong-field-seeking polar
molecules at 30 m/s (kinetic energy of 2K) and hold them, for several minutes,
against losses due to defocusing, oscillations, and diffusion. The ring, 3 m in
diameter, has straight sections that afford access to the stored molecules and
a lattice structure that may be adapted for evaporative cooling. Simulation is
done using a newly-developed code that tracks the particles, in time, through
400 turns; it accounts for longitudinal velocity changes as a function of
external electric field, focusing and deflection nonlinearities, and the
effects of gravity. An injector, decelerator, and source are included and
intensities are calculated.Comment: 6 pages 5 figures, 3 table
Generation of large flavor mixing from radiative corrections
We provide a model independent criterion which would guarantee a large flavor
mixing of two quasi-degenerate Majorana neutrinos at the low scale,
irrespective of the mixing at the high scale. We also show that such a
situation is realizable for a phenomenologically interesting range of
parameters of the weak scale theory. We further show that for a similar
condition to be implementable for the three generation case, the CP parity of
one of the neutrinos needs to be opposite to that of the others.Comment: 14 pages RevTeX, 2 eps figures. Minor changes made, a few references
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Suppression of inelastic collisions of polar state molecules in an electrostatic field
Collisions of polar state molecules at ultralow energies are
considered, within a model that accounts for long-range dipole-dipole
interactions, plus rotation of the molecules. We predict a substantial
suppression of dipole-driven inelastic collisions at high values of the applied
electric field, namely, field values of several times . Here is
the rotational constant, and is the electric dipole moment of molecules.
The sudden large drop in the inelastic cross section is attributed to the
onset of degeneracy between molecular rotational levels, which dramatically
alters the scattering Hamiltonian. As a result of the large ratio of elastic to
inelastic collision rates, we predict that evaporative cooling may be feasible
for state molecules in weak-field-seeking states, provided a large
bias electric field is present
Lepton Flavor Violation at the LHC
Recent results from Super Kamiokande suggest mixing and
hence lepton flavor violation. In supersymmetric models, this flavor violation
may have implications for the pattern of slepton masses and mixings. Possible
signals for this mixing in the decays of sleptons produced at the LHC are
discussed. The sensitivity expected is compared to that of rare decays such as
.Comment: 14 pages, 9 figure
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