29,933 research outputs found
Eimeria tenella protein trafficking: differential regulation of secretion versus surface tethering during the life cycle
Eimeria spp. are intracellular parasites that have a major impact on poultry. Effective live vaccines are available and the development of reverse genetic technologies has raised the prospect of using Eimeria spp. as recombinant vectors to express additional immunoprotective antigens. To study the ability of Eimeria to secrete foreign antigens or display them on the surface of the sporozoite, transiently transfected populations of E. tenella expressing the fluorescent protein mCherry, linked to endogenous signal peptide (SP) and glycophosphatidylinositol-anchor (GPI) sequences, were examined. The SP from microneme protein EtMIC2 (SP2) allowed efficient trafficking of mCherry to cytoplasmic vesicles and following the C-terminal addition of a GPI-anchor (from surface antigen EtSAG1) mCherry was expressed on the sporozoite surface. In stable transgenic populations, mCherry fused to SP2 was secreted into the sporocyst cavity of the oocysts and after excystation, secretion was detected in culture supernatants but not into the parasitophorous vacuole after invasion. When the GPI was incorporated, mCherry was observed on the sporozites surface and in the supernatant of invading sporozoites. The proven secretion and surface exposure of mCherry suggests that antigen fusions with SP2 and GPI of EtSAG1 may be promising candidates to examine induction of protective immunity against heterologous pathogens
Single and Many Particle Correlation Functions and Uniform Phase Bases for Strongly Correlated Systems
The need for suitable many or infinite fermion correlation functions to
describe some low dimensional strongly correlated systems is discussed. This is
linked to the need for a correlated basis, in which the ground state may be
postive definite, and in which single particle correlations may suffice. A
particular trial basis is proposed, and applied to a certain quasi-1D model.
The model is a strip of the 2D square lattice wrapped around a cylinder, and is
related to the ladder geometries, but with periodic instead of open boundary
conditions along the edges. Analysis involves a novel mean-field approach and
exact diagonalisation. The model has a paramagnetic region and a Nagaoka
ferromagnetic region. The proposed basis is well suited to the model, and
single particle correlations in it have power law decay for the paramagnet,
where the charge motion is qualitatively hard core bosonic. The mean field also
leads to a BCS-type model with single particle long range order.Comment: 23 pages, in plain tex, 12 Postscript figures included. Accepted for
publication in J.Physics : Condensed Matte
The Higgs Sector of the Minimal 3 3 1 Model Revisited
The mass spectrum and the eigenstates of the Higgs sector of the minimal 3 3
1 model are revisited in detail. There are discrepancies between our results
and previous results by another author.Comment: 20 pages, latex, two figures. One note and one reference are adde
Using Muonic Hydrogen in Optical Spectroscopy Experiment to Detect Extra Dimensions
Considering that gravitational force might deviate from Newton's
inverse-square law (ISL) and become much stronger in small scale, we propose a
kind of optical spectroscopy experiment to detect this possible deviation and
take electronic, muonic and tauonic hydrogen atoms as examples. This experiment
might be used to indirectly detect the deviation of ISL down to nanometer scale
and to explore the possibility of three extra dimensions in ADD's model, while
current direct gravity tests cannot break through micron scale and go beyond
two extra dimensions scenario.Comment: 9 pages, 2 figures. To appear in IJT
Valley Splitting Theory of SiGe/Si/SiGe Quantum Wells
We present an effective mass theory for SiGe/Si/SiGe quantum wells, with an
emphasis on calculating the valley splitting. The theory introduces a valley
coupling parameter, , which encapsulates the physics of the quantum well
interface. The new effective mass parameter is computed by means of a tight
binding theory. The resulting formalism provides rather simple analytical
results for several geometries of interest, including a finite square well, a
quantum well in an electric field, and a modulation doped two-dimensional
electron gas. Of particular importance is the problem of a quantum well in a
magnetic field, grown on a miscut substrate. The latter may pose a numerical
challenge for atomistic techniques like tight-binding, because of its
two-dimensional nature. In the effective mass theory, however, the results are
straightforward and analytical. We compare our effective mass results with
those of the tight binding theory, obtaining excellent agreement.Comment: 13 pages, 7 figures. Version submitted to PR
Local spin fluctuations in iron-based superconductors: 77Se and 87Rb NMR measurements of Tl0.47Rb0.34Fe1.63Se2
We report nuclear magnetic resonance (NMR) studies of the intercalated iron
selenide superconductor (Tl, Rb)FeSe ( K).
Single-crystal measurements up to 480 K on both Se and Rb nuclei
show a superconducting phase with no magnetic order. The Knight shifts and
relaxation rates increase very strongly with temperature above ,
before flattening at 400 K. The quadratic -dependence and perfect
proportionality of both and data demonstrate their origin in
paramagnetic moments. A minimal model for this pseudogap-like response is not a
missing density of states but two additive contributions from the itinerant
electronic and local magnetic components, a framework unifying the and
data in many iron-based superconductors
Effects of dynamical phases in Shor's factoring algorithm with operational delays
Ideal quantum algorithms usually assume that quantum computing is performed
continuously by a sequence of unitary transformations. However, there always
exist idle finite time intervals between consecutive operations in a realistic
quantum computing process. During these delays, coherent "errors" will
accumulate from the dynamical phases of the superposed wave functions. Here we
explore the sensitivity of Shor's quantum factoring algorithm to such errors.
Our results clearly show a severe sensitivity of Shor's factorization algorithm
to the presence of delay times between successive unitary transformations.
Specifically, in the presence of these {\it coherent "errors"}, the probability
of obtaining the correct answer decreases exponentially with the number of
qubits of the work register. A particularly simple phase-matching approach is
proposed in this paper to {\it avoid} or suppress these {\it coherent errors}
when using Shor's algorithm to factorize integers. The robustness of this
phase-matching condition is evaluated analytically or numerically for the
factorization of several integers: , and 33.Comment: 8 pages with 5 figure
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