8,474 research outputs found
Surface immobilization of hexa-histidine-tagged adeno-associated viral vectors for localized gene delivery.
Adeno-associated viral (AAV) vectors, which are undergoing broad exploration in clinical trials, have significant promise for therapeutic gene delivery because of their safety and delivery efficiency. Gene delivery technologies capable of mediating localized gene expression may further enhance the potential of AAV in a variety of therapeutic applications by reducing spread outside a target region, which may thereby reduce off-target side effects. We have genetically engineered an AAV variant capable of binding to surfaces with high affinity through a hexa-histidine metal-binding interaction. This immobilized AAV vector system mediates high-efficiency delivery to cells that contact the surface and thus may have promise for localized gene delivery, which may aid numerous applications of AAV delivery to gene therapy
Integer quantum Hall effect on a six valley hydrogen-passivated silicon (111) surface
We report magneto-transport studies of a two-dimensional electron system
formed in an inversion layer at the interface between a hydrogen-passivated
Si(111) surface and vacuum. Measurements in the integer quantum Hall regime
demonstrate the expected sixfold valley degeneracy for these surfaces is
broken, resulting in an unequal occupation of the six valleys and anisotropy in
the resistance. We hypothesize the misorientation of Si surface breaks the
valley states into three unequally spaced pairs, but the observation of odd
filling factors, is difficult to reconcile with non-interacting electron
theory.Comment: 4 pages, 4 figures, to appear in Physical Review Letter
Resonant Tunneling Between Quantum Hall Edge States
Resonant tunneling between fractional quantum Hall edge states is studied in
the Luttinger liquid picture. For the Laughlin parent states, the resonance
line shape is a universal function whose width scales to zero at zero
temperature. Extensive quantum Monte Carlo simulations are presented for which confirm this picture and provide a parameter-free prediction for the
line shape.Comment: 14 pages , revtex , IUCM93-00
The effect of inter-edge Coulomb interactions on the transport between quantum Hall edge states
In a recent experiment, Milliken {\em et al.} demonstrated possible evidence
for a Luttinger liquid through measurements of the tunneling conductance
between edge states in the quantum Hall plateau. However, at low
temperatures, a discrepancy exists between the theoretical predictions based on
Luttinger liquid theory and experiment. We consider the possibility that this
is due to long-range Coulomb interactions which become dominant at low
temperatures. Using renormalization group methods, we calculate the cross-over
behaviour from Luttinger liquid to the Coulomb interaction dominated regime.
The cross-over behaviour thus obtained seems to resolve one of the
discrepancies, yielding good agreement with experiment.Comment: 4 pages, RevTex, 2 postscript figures, tex file and figures have been
uuencode
Correlation effects of carbon nanotubes at boundaries: Spin polarization induced by zero-energy boundary states
When a carbon nanotube is truncated with a certain type of edges, boundary
states localized near the edges appear at the fermi level. Starting from
lattice models, low energy effective theories are constructed which describe
electron correlation effects on the boundary states. We then focus on a thin
metallic carbon nanotube which supports one or two boundary states, and discuss
physical consequences of the interaction between the boundary states and bulk
collective excitations. By the renormalization group analyses together with the
open boundary bosonization, we show that the repulsive bulk interactions
suppress the charge fluctuations at boundaries, and assist the spin
polarization.Comment: 8 pages, 1 figur
Dynamical electron transport through a nanoelectromechanical wire in a magnetic field
We investigate dynamical transport properties of interacting electrons moving
in a vibrating nanoelectromechanical wire in a magnetic field. We have built an
exactly solvable model in which electric current and mechanical oscillation are
treated fully quantum mechanically on an equal footing. Quantum mechanically
fluctuating Aharonov-Bohm phases obtained by the electrons cause nontrivial
contribution to mechanical vibration and electrical conduction of the wire. We
demonstrate our theory by calculating the admittance of the wire which are
influenced by the multiple interplay between the mechanical and the electrical
energy scales, magnetic field strength, and the electron-electron interaction
Interaction effects in multi-subband quantum wires
We investigate the effect of electron-electron interactions on the transport
properties of disordered quasi one-dimensional quantum wires with two or more
subbands occupied. We apply two alternative methods to solve the logarithmic
divergent problem, namely the parquet graph theory and a renormalization group
calculation. We solve the group equations analytically in the weak coupling
limit and find a power-law for the temperature dependent conductivity of a
multi-channel system. The exponent is roughly equal to the inverse of the
number of the occupied subbands.Comment: 4 pages, style-files included. No figure. Appears in J. Phys. Soc.
Japan (Letter
Scaling and non-Abelian signature in fractional quantum Hall quasiparticle tunneling amplitude
We study the scaling behavior in the tunneling amplitude when quasiparticles
tunnel along a straight path between the two edges of a fractional quantum Hall
annulus. Such scaling behavior originates from the propagation and tunneling of
charged quasielectrons and quasiholes in an effective field analysis. In the
limit when the annulus deforms continuously into a quasi-one-dimensional ring,
we conjecture the exact functional form of the tunneling amplitude for several
cases, which reproduces the numerical results in finite systems exactly. The
results for Abelian quasiparticle tunneling is consistent with the scaling
anaysis; this allows for the extraction of the conformal dimensions of the
quasiparticles. We analyze the scaling behavior of both Abelian and non-Abelian
quasiparticles in the Read-Rezayi Z_k-parafermion states. Interestingly, the
non-Abelian quasiparticle tunneling amplitudes exhibit nontrivial k-dependent
corrections to the scaling exponent.Comment: 16 pages, 4 figure
Randomness at the Edge: Theory of Quantum Hall transport at filling
Current Luttinger liquid edge state theories for filling predict a
non-universal Hall conductance, in disagreement with experiment. Upon inclusion
of random edge tunnelling we find a phase transition into a new
disordered-dominated edge phase. An exact solution of the random model in this
phase gives a quantized Hall conductance of 2/3 and a neutral mode propagating
upstream. The presence of the neutral mode changes the predicted temperature
dependence for tunnelling through a point contact from to .Comment: 12 pages 1 postscript figure appended, REVTEX 3.
Anomalous tunneling conductances of a spin singlet \nu=2/3 edge states: Interplay of Zeeman splitting and Long Range Coulomb Interaction
The point contact tunneling conductance between edges of the spin singlet
quantum Hall states is studied both in the
quasiparticle tunneling picture and in the electron tunneling picture. Due to
the interplay of Zeeman splitting and the long range Coulomb interaction
between edges of opposite chirality novel spin excitations emerge, and their
effect is characterized by anomalous exponents of the charge and spin tunneling
conductances in various temperature ranges. Depending on the kinds of
scatterings at the point contact and the tunneling mechanism the anomalous
interaction in spin sector may enhance or suppress the tunneling conductances.
The effects of novel spin excitation are also relevant to the recent NMR
experiments on quantum Hall edges.Comment: Revtex File, 7 pages: To be published in Physical Reviews
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