7,331 research outputs found
Kaluza-Klein Structure Associated With Fat Brane
It is known that the imposition of orbifold boundary conditions on background
scalar field can give rise to a non-trivial vacuum expectation value (VEV)
along extra dimensions, which in turn generates fat branes and associated
unconventional Kaluza-Klein (KK) towers of fermions. We study the structure of
these KK towers in the limit of one large extra dimension and show that
normalizable (bound) states of massless and massive fermions can exist at both
orbifold fixed points. Closer look however indicates that orbifold boundary
conditions act to suppress at least half of bound KK modes, while periodic
boundary conditions tend to drive the high-lying modes to the conventional
structure. By investigating the scattering of fermions on branes, we
analytically compute masses and wavefunctions of KK spectra in the presence of
these boundary conditions up to one-loop level. Implication of KK-number
non-conservation couplings on the Coulomb potential is also examined.Comment: RevTex4, 29 pages, 7 ps figures, new references adde
Mitf-Mdel, a novel melanocyte/melanoma-specific isoform of microphthalmia-associated transcription factor-M, as a candidate biomarker for melanoma
<p>Abstract</p> <p>Background</p> <p>Melanoma incidence is on the rise and advanced melanoma carries an extremely poor prognosis. Treatment options, including chemotherapy and immunotherapy, are limited and offer low response rates and transient efficacy. Thus, identification of new melanocyte/melanoma antigens that serve as potential novel candidate biomarkers in melanoma is an important area for investigation.</p> <p>Methods</p> <p>Full length MITF-M and its splice variant cDNA were cloned from human melanoma cell line 624 mel by reverse transcription polymerase chain reaction (RT-PCR). Expression was investigated using regular and quantitative RT-PCR in three normal melanocytes (NHEM), 31 melanoma cell lines, 21 frozen melanoma tissue samples, 18 blood samples (pheripheral blood mononuclear cell; PBMC) from healthy donors and 12 non-melanoma cancer cell lines, including three breast, five glioma, one sarcoma, two kidney and one ovarian cancer cell lines.</p> <p>Results</p> <p>A novel splice variant of MITF-M, which we named MITF-Mdel, was identified. The predicted MITF-Mdel protein contains two in frame deletions, 56- and 6- amino acid deletions in exon 2 (from V32 to E87) and exon 6 (from A187 to T192), respectively. MITF-Mdel was widely expressed in melanocytes, melanoma cell lines and tissues, but almost undetectable in non-melanoma cell lines or PBMC from healthy donors. Both isoforms were expressed significantly higher in melanoma tissues than in cell lines. Two of 31 melanoma cell lines expressed only one isoform or the other.</p> <p>Conclusion</p> <p>MITF-Mdel, a novel melanocyte/melanoma-specific isoform of MITF-M, may serve as a potential candidate biomarker for diagnostic and follow-up purposes in melanoma.</p
Fragmented superfluid due to frustration of cold atoms in optical lattices
A one dimensional optical lattice is considered where a second dimension is
encoded in the internal states of the atoms giving effective ladder systems.
Frustration is introduced by an additional optical lattice that induces
tunneling of superposed atomic states. The effects of frustration range from
the stabilization of the Mott insulator phase with ferromagnetic order, to the
breakdown of superfluidity and the formation of a macroscopically fragmented
phase.Comment: New version, more results, about 20 page
Anisotropic Pauli Spin Blockade of Holes in a GaAs Double Quantum Dot
Electrically defined semiconductor quantum dots are attractive systems for spin
manipulation and quantum information processing. Heavy-holes in both Si and GaAs
are promising candidates for all-electrical spin manipulation, owing to the weak hyper-
fine interaction and strong spin-orbit interaction. However, it has only recently become
possible to make stable quantum dots in these systems, mainly due to difficulties in
device fabrication and stability. Here we present electrical transport measurements on
holes in a gate-defined double quantum dot in a GaAs/AlxGa1−xAs heterostructure.
We observe clear Pauli spin blockade and demonstrate that the lifting of this spin
blockade by an external magnetic field is highly anisotropic. Numerical calculations of
heavy-hole transport through a double quantum dot in the presence of strong spin-orbit
coupling show quantitative agreement with experimental results and suggest that the
observed anisotropy can be explained by both the anisotropic effective hole g-factor
and the surface Dresselhaus spin-orbit interaction
A Model of Quark and Lepton Masses I: The Neutrino Sector
If neutrinos have masses, why are they so tiny? Are these masses of the Dirac
type or of the Majorana type? We are already familiar with the mechanism of how
to obtain a tiny Majorana neutrino mass by the famous see-saw mechanism. The
question is: Can one build a model in which a tiny Dirac neutrino mass arises
in a more or less "natural" way? What would be the phenomenological
consequences of such a scenario, other than just merely reproducing the
neutrino mass patterns for the oscillation data? In this article, a systematic
and detailed analysis of a model is presented, with, as key components, the
introduction of a family symmetry as well as a new SU(2) symmetry for the
right-handed neutrinos. In particular, in addition to the calculations of light
neutrino Dirac masses, interesting phenomenological implications of the model
will be presented.Comment: 25 (single-spaced) pages, 11 figures, corrected some typos in Table
I, added acknowledgement
Single-Atom Resolved Fluorescence Imaging of an Atomic Mott Insulator
The reliable detection of single quantum particles has revolutionized the
field of quantum optics and quantum information processing. For several years,
researchers have aspired to extend such detection possibilities to larger scale
strongly correlated quantum systems, in order to record in-situ images of a
quantum fluid in which each underlying quantum particle is detected. Here we
report on fluorescence imaging of strongly interacting bosonic Mott insulators
in an optical lattice with single-atom and single-site resolution. From our
images, we fully reconstruct the atom distribution on the lattice and identify
individual excitations with high fidelity. A comparison of the radial density
and variance distributions with theory provides a precise in-situ temperature
and entropy measurement from single images. We observe Mott-insulating plateaus
with near zero entropy and clearly resolve the high entropy rings separating
them although their width is of the order of only a single lattice site.
Furthermore, we show how a Mott insulator melts for increasing temperatures due
to a proliferation of local defects. Our experiments open a new avenue for the
manipulation and analysis of strongly interacting quantum gases on a lattice,
as well as for quantum information processing with ultracold atoms. Using the
high spatial resolution, it is now possible to directly address individual
lattice sites. One could, e.g., introduce local perturbations or access regions
of high entropy, a crucial requirement for the implementation of novel cooling
schemes for atoms on a lattice
Pion Propagation near the QCD Chiral Phase Transition
We point out that, in analogy with spin waves in antiferromagnets, all
parameters describing the real-time propagation of soft pions at temperatures
below the QCD chiral phase transition can be expressed in terms of static
correlators. This allows, in principle, the determination of the soft pion
dispersion relation on the lattice. Using scaling and universality arguments,
we determine the critical behavior of the parameters of pion propagation. We
predict that when the critical temperature is approached from below, the pole
mass of the pion drops despite the growth of the pion screening mass. This fact
is attributed to the decrease of the pion velocity near the phase transition.Comment: 8 pages (single column), RevTeX; added references, version to be
published in PR
Elliptical flow -- a signature for early pressure in ultrarelativistic nucleus-nucleus collisions
Elliptical energy flow patterns in non-central Au(11.7AGeV) on Au reactions
have been studied employing the RQMD model. The strength of these azimuthal
asymmetries is calculated comparing the results in two different modes of RQMD
(mean field and cascade). It is found that the elliptical flow which is readily
observable with current experimental detectors may help to distinguish
different reasonable expansion scenarios for baryon-dense matter. The final
asymmetries are very sensitive to the pressure at maximum compression, because
they involve a partial cancelation between early squeeze-out and subsequent
flow in the reaction plane. This cancelation can be expected to occur in a
broad energy region covered by the current heavy ion fixed-target programs at
BNL and at CERN.Comment: 14 pages LaTeX including 3 postscript figure
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